bluuebunny/crossref_metadata_2025 huggingface dataset:
Intra- and extravascular turnover of thyrotrophin-releasing hormone in normal man
Authors: Iversen E.
Published: December 2008

In 14 normal subjects constant TRH infusions for determination of plasma clearance rate (PCR) and half-life of disappearance (t½) of TRH were carried out with simultaneous determination of half-life of disappearance of TRH in serum in vitro (t½p). PCR, t½ and t½p were 1532 ± 423 ml/min, 6·6 ± 1·5 min and 16·8 ± 9·4 min respectively (mean ± s.d.) and displayed only minor fluctuations when determined repeatedly in the same subjects (coefficients of variation within individuals were 15·1, 10·6 and 7·5% respectively). Simultaneous determination of PCR, t½ and t½p enabled calculation of the half-life of disappearance of TRH in the extravascular tissue compartment (t½t). Values of t½t (6·3 ± 1·4 min) correlated to t½p (r = 0·95). Activities of TRH-degrading enzymes in tissues and in serum were independent of sex, phase of female menstrual cycle, time of day and of the concentrations of TRH used. The methods employed for this investigation offer the possibility of examining the degradation of TRH and TRH analogues both in the serum and in the extravascular compartment during various conditions.

J. Endocr. (1988) 118, 511–516
SECRETION OF β-ENDORPHIN INTO THE MATERNAL CIRCULATION BY UTEROPLACENTAL TISSUES IN RESPONSE TO HYPOGLYCAEMIC STRESS
Authors: Falconer J. , Chan E.-C. , Madsen G. , Thomson M. , Davies J. , Smith R.
Published: December 2008

The placenta has been shown to contain ACTH and β-endorphin but the roles of these peptides are unknown. To investigate whether they are released into the maternal circulation from the placenta in response to physiological stimuli the effects of hypoglycaemic stress were investigated. Plasma samples were collected from the femoral artery (FA) and uterovarian (UV) vein of nine pregnant sheep before and during hypoglycaemia induced by intravenous insulin (100U). Plasma concentrations of ovine β-endorphin (oβ-EP) were measured by radioimmunoassay. Concentrations of oβ-EP rose in both vessels by 60 min after insulin. The peak concentrations of oβ-EP (pmol/l) were 122 ± 29 (mean ± SEM, n=8) in the UV and 96±24 (n=9) fmol/ml in the FA 60 min after insulin injection. There was no difference between the concentrations of oβ-EP in the vessels before insulin injection but at 60 and 120 min after insulin the concentrations of oβ-EP were significantly higher in the UV than FA (P<0.02, analysis of variance). This indicates that the pregnant uterus or placenta can respond to hypoglycaemia by secreting β-EP into the maternal circulation. It is therefore possible that placental pro-opiomelanocortin (POMC) peptides may have a role in maternal endocrinology and metabolism.
IS OXYTOCIN OF CONCEPTUS ORIGIN INVOLVED IN INHIBITION OF LUTEAL REGRESSION IN EARLY PREGNANCY IN EWES?
Authors: Lacroix M.C. , Charpigny G. , Reinaud P.
Published: December 2008

This study describes the presence in and production by the ovine conceptus of an oxytocin-like peptide during the early stages of development. Oxycotin was measured by radioimmunoassay in ovine conceptuses from days 14 to 30 of pregnancy. Tissue concentrations of oxytocin increased from day 14 (24.8 ± 5 pg/100 mg) until day 19 (122.9 ± 52 pg/100 mg) and then decreased (3 ± 1 pg /100 mg). Oxytocin was released into culture medium by day-15 ovine conceptuses at a rate of 262 ± 55 pg/24 h. Reverse-phase high-performance liquid chromatography (HPLC) analysis of peptides extracted from a pool of ovine conceptuses was conducted using chromatographic conditions developed to separate oxytocin from other nonapeptides. Radioimmunoassay of HPLC fractions for oxytocin revealed an immunoactive conceptus peptide in a single fraction at the same retention time as chromatographed authentic oxytocin. Radioimmunoassay and chromatographic data therefore suggest that this oxytocin-like peptide is similar, if not identical, to authentic oxytocin. Concentrations of oxytocin in conceptus tissue were maximal during the period of inhibition of luteal regression (days 14-19). It is proposed that conceptus oxytocin is involved in the maintenance of luteal function in early pregnancy.
Increase in plasma concentrations of atrial natriuretic peptide during infusion of hypertonic saline in conscious newborn calves
Authors: Amadieu-Farmakis M. , Giry J. , Barlet J.-P.
Published: December 2008

Plasma concentrations of atrial natriuretic peptide (ANP), plasma renin activity (PRA), plasma concentrations of aldosterone, urine flow rate and sodium and potassium excretion were studied in two groups of four conscious 3-day-old male calves, infused with hypertonic saline or vehicle. Hypertonic saline infusion (20 mmol NaCl/kg body weight) was accompanied by a progressive rise in plasma concentrations of ANP (from 16·5 ± 0·2 pmol/l at time 0 to 29·3 ± 3·0 pmol/l at 30 min; P< 0·05) and by a gradual decrease in PRA (from 1·61±0·23 nmol angiotensin I/1 per h at time 0 to 0·54± 15 nmol angiotensin I/1 per h at 90 min; P<0·05); there was no change in the plasma concentration of aldosterone. Within the first 2 h of the 24-h urine collection period there was a marked rise in urine flow rate and sodium excretion in treated calves when compared with control animals (66·0 ± 8·3 vs 15·9±1·2 ml/kg body weight per 2 h (P<0·05) and 6·7±1·3 vs 0·4±0·02 mmol/kg body weight per 2 h (P<0·01) respectively). During the following 22 h, urinary water and sodium excretion remained at significantly high levels.

Thus, in the conscious newborn calf, changes in plasma ANP levels and urinary water and sodium excretion during hypertonic saline infusion are compatible with the hypothesis that endogenous ANP participates, at least in part, in the immediate diuretic and natriuretic renal response induced by the sodium overload.

J. Endocr. (1988) 119, 23–29
Diminution of pulsatile growth hormone secretion in the domestic fowl (Gallus domesticus): evidence of sexual dimorphism
Authors: Johnson R. J.
Published: December 2008

Temporal plasma GH secretory patterns were measured in cannulated male and female meat-type chickens of two commercial strains at 17, 38 and 60 days of age. Pulse height, amplitude and baseline values were similar in both male and female chickens at 17 days of age, with high amplitude and low baseline values. However, by 38 days of age pulsatile GH secretion was not detectable in females, whereas males exhibited a continued pulsatile secretory pattern similar to that at 17 days of age. Pulsatile GH secretion was not evident in either males or females at 60 days of age. These results clearly demonstrate a sexually dimorphic ontogeny of GH secretion in meat-type chickens.

J. Endocr. (1988) 119, 101–109
Comparison of some biological effects of epidermal growth factor and commercial serum albumin on the induction of α-lactalbumin in rat and rabbit mammary explants
Authors: Nicholas K. R. , Sankaran L. , Kulski J. K. , Chomczynski P. , Qasba P.
Published: December 2008

Commercial preparations of serum albumin from six species can markedly enhance the prolactin-independent induction of α-lactalbumin in mammary explants from pregnant rats, and evoke such induction in the tissue from virgin rats. These effects are similar to those of epidermal growth factor (EGF) reported previously. The stimulatory activity of bovine serum albumin (BSA) resides in a putative impurity in the albumin. Charcoal extraction and gel filtration of the BSA results in complete loss of activity. Of the five milk protein mRNAs studied, only α-lactalbumin mRNA is induced by insulin, glucocorticoid and serum albumin in the absence of prolactin. Despite these similarities, the biological effects of serum albumin and EGF on mammary tissue diverge in some respects. They appear to operate by different mechanisms since their effects on the rat system are additive. Furthermore, while both inhibit prolactin-mediated induction of α-lactalbumin in rabbit mammary explants, cortisol converts EGF into a stimulatory agent, but merely blocks the inhibitory effect of serum albumin. The results emphasize that commercial serum albumin is not to be regarded simply as an inert protein additive to culture media.

J. Endocr. (1988) 119, 133–139
Pregnanediol excretion in fertile women: age-related changes
Authors: Metcalf M. G. , Livesey J. H.
Published: December 2008

In normal women reproductive capacity diminishes with age; the decline has been detected before the start of the menopausal transition. It is known that in premenopausal women most menstrual cycles are ovulatory. An investigation was set up to examine the possibility that there is an age-related decline in the ability of the corpus luteum to secrete progesterone at this time.

Once-weekly urine samples for the measurement of pregnanediol were collected from 100 women aged 20–48 years, all of whom had regular 20- to 35–day menstrual cycles (1124 samples collected during the course of 312 menstrual cycles of which 96·8% were ovulatory). Pregnanediol excretion rates parallel the levels of progesterone in plasma. Examination of the rank correlation between age and pregnanediol excretion identified a significant negative correlation during the early and mid-follicular phases, but failed to detect any age-related change during the luteal phase.

The evidence does not support the concept of an age-related increase in luteal phase defects before the start of the menopausal transition.

J. Endocr. (1988) 119, 153–157
Characterization of circulating pro-opiomelanocortin-related peptides in human septic shock
Authors: McLoughlin L. , Evans S. F. , Watson J. D. , Hinds C. J. , Rees L. H.
Published: December 2008

The nature of circulating pro-opiomelanocortin (POMC)-related peptides was investigated in patients with a diagnosis of septic shock. Also, changes following administration of methylprednisolone were monitored using established chromatographic techniques and three radioimmunoassays directed towards the N-terminal, mid-portion and C-terminal regions of the precursor.

Adrenocorticotrophin and β-endorphin-like peptides were identified in the circulation. By 60 min after a pharmacological dose of methylprednisolone (30 mg/kg) concentrations of these peptides were reduced and continued to fall up to 180 min. β-Lipotrophin and N-terminal POMC(1–76) were also detected by the β-endorphin and γ3-MSH assays respectively. The concentrations of these peptides were noticeably reduced only after 180 min.

The 31 000 Da MSH/ACTH/β-endorphin (POMC) and the 22 000 Da MSH/ACTH precursors were also present in the circulation in septic shock and their concentrations increased following steroid treatment.

J. Endocr. (1988) 119, 159–165
Relationship between zonal distribution of microsomal cytochrome P-450s (P-45017α,lyase and P-450C21) and steroidogenic activities in guinea-pig adrenal cortex
Authors: Shinzawa K. , Ishibashi S. , Murakoshi M. , Watanabe K. , Kominami S. , Kawahara A. , Takemori S.
Published: December 2008

In an attempt to elucidate the functional role of the three zones of the adrenal cortex, the localization of microsomal cytochrome P-450s (P-45017α,lyase and P-450C21) and their relation to steroidogenesis in the guinea-pig adrenal cortex were studied. The intracellular localization and zonal distribution of P-45017α,lyase and P-450C21 were examined by the direct peroxidase-labelled antibody technique. The cytochromes were localized immunocytochemically on the smooth-surfaced endoplasmic reticulum. P-45017α,lyase was found to be distributed in the zona fasciculata, especially in the externa, and less in the zona reticularis. The zona glomerulosa was negative for immunohistochemical staining for P-45017α,lyase. In contrast, P-450C21 was distributed in all three zones in the adrenal cortex.

The cytochrome P-450 contents and their steroidogenic activities were determined with microsomes prepared from the outer zone (zonae glomerulosa and fasciculata) and from the inner zone (zona reticularis) of guinea-pig adrenals. Using an enzyme-linked immunosorbent assay, the ratio of P-450C21 content in the inner zone to that in the outer zone microsomes was estimated to be 1 ·24. 21-Hydroxylase activity was higher in the inner zone microsomes, which was in good agreement with the relative P-450C21 contents. The ratio of P-45017α,lyase content in the inner zone to that in the outer zone microsomes was estimated to be 0·75. 17α-Hydroxylase and C17–20-lyase activities were five- to sixfold greater in the outer than in the inner zone microsomes, which could not be explained by the P-45017α,lyase contents in the two zones.

The effects of ACTH on the zonal distribution of microsomal cytochrome P-450s and their steroidogenic activities were also investigated.

J. Endocr. (1988) 119, 191–200
Evidence of a functional aromatase system in the pituitary gland of the chick embryo in vitro
Authors: Guennoun R. , Gasc J.-M.
Published: December 2008

The in-vitro effects of oestradiol and testosterone, alone or together with an aromatase inhibitor (1,4,6-androstatriene-3,17-dione), on the appearance of progesterone receptor (PR) in the pituitary were studied in the chick embryo. Whole pituitary glands from 10-day-old embryos were cultured for 2 days in a hormonally defined medium. The oestrogenic activity of the hormone added to the medium was determined by the induction of PR in nuclei of pituitary cells. Cells containing PR were identified by immunohistochemistry with an antibody to PR. Pituitary cells contained PR in their nuclei after 48 h of incubation with oestradiol or testosterone (0·1 μmol/l). Dihydrotestosterone failed to induce PR in pituitary cells, as did testosterone if the aromatase inhibitor was added to the culture medium. It is concluded that testosterone is aromatized locally at the level of the pituitary and, consequently, acts through the oestradiol receptor to induce the appearance of PR in pituitary cells.

J. Endocr. (1988) 119, 229–232
Early secretion of chorionic gonadotrophin by marmoset embryos in vivo and in vitro
Authors: Hearn J. P. , Hodges J. K. , Gems S.
Published: December 2008

The control mechanisms of early pregnancy in primates differ from those in non-primate species in the early secretion of chorionic gonadotrophin (CG) by the embryo and in the support of the corpus luteum. This study describes the initiation of secretion of CG by the embryo of the marmoset monkey examined in vivo and in vitro. A bioassay for gonadotrophin, which did not distinguish between CG and LH, was adapted and validated for the marmoset. A system of embryo culture was developed whereby embryos were grown from morula/blastocyst stages until at least the differentiation of the trophoblast and yolk sac, facilitated by the embryo attaching to a monolayer of marmoset fibroblast cells. Gonadotrophin concentrations were measured in the peripheral circulation of marmosets during precisely timed stages during the first 84 days of the 144-day gestation period, providing a profile of secretion that was maintained at high levels for longer than the profile seen in Old World primates, including man. A clear increase above baseline levels was seen by day 17 after ovulation, implantation commencing in the marmoset on days 11–13. Gonadotrophin was secreted by embryos in culture from the time of attachment in vitro, but there was no clear evidence of secretion before attachment. Levels of gonadotrophin secreted by embryos in vitro increased rapidly, reaching a maximum mean production rate of 90 mIU/24 h within 4 days after attachment. The experimental systems developed here will allow the examination of the local function of CG at the implantation site, intra-embryonic control of its secretion and its possible involvement in embryonic development.

J. Endocr. (1988) 119, 249–255
Increases in plasma concentrations of steroids in the rat after the administration of caffeine: comparison with plasma disposition of caffeine
Authors: Pollard I.
Published: December 2008

It was demonstrated that the altered endocrine environment caused by caffeine consumption could be equated with a stress-like pattern of response. A single acute treatment with caffeine (30 or 60 mg/kg) to male rats approximately 85 days old caused plasma concentrations of corticosterone, progesterone, testosterone and Na+ to rise significantly above control values. These changes were evident 3 min after caffeine administration and were maintained for 1–4 h before returning to normal. In animals exposed to daily chronic caffeine treatment for 10 days or more the levels of progesterone fell and Na+ rose significantly compared with control values at 24 h after administration. Following a single treatment of 30 mg/kg, caffeine was detected in blood plasma after 3 min, and reached peak levels by 1 h. After 24 h, less than 2% of the peak levels of caffeine remained. Metabolites of caffeine were detectable within 6 min and reached their peak levels 4 and 12 h later for theophylline and theobromine respectively.

It is suggested that high steroid levels may in the long-term cause an altered hepatic clearance pattern affecting both steroid metabolism and caffeine elimination. A preliminary study of the morphology of livers from males chronically exposed to caffeine revealed that the hepatic cells lost cytoplasmic matrix, and that the sinusoids did not show up as clear spaces, compared with those in the controls.

J. Endocr. (1988) 119, 275–280
Failure of acid–ethanol treatment to prevent interference by binding proteins in radioligand assays for the insulin-like growth factors
Authors: Mesiano S. , Young I. R. , Browne C. A. , Thorburn G. D.
Published: December 2008

Acid–ethanol precipitation and gel filtration at acidic pH have been widely used to extract circulating binding proteins for insulin-like growth factor (IGF-I and IGF-II) from plasma or serum samples before radioligand assay for the respective IGFs. Gel filtration on Sephadex G-50 at neutral pH of neutralized acid– ethanol extracts of fetal and adult ovine plasma which had been incubated with 125I-labelled IGF-I or 125I-labelled IGF-II revealed that significant amounts of the IGF-binding protein activity survived the acid– ethanol extraction procedure.

Radioimmunoassay for IGF-I in acid–ethanol extracts of plasma samples from fetal, neonatal and adult sheep yielded results which depended upon the method used for separation of the antibody-bound IGF-I tracer from the free IGF-I tracer. Acid gel filtration of ovine fetal and adult plasma was found to remove completely the IGF-binding protein activity. Radioimmunoassay for IGF-I in samples of fetal, neonatal and adult sheep plasma that had undergone acid gel chromatography yielded consistent results for both methods that were used to separate antibody-bound IGF-I tracer from the free tracer.

Radioreceptor assays for IGF-II were similarly highly perturbed by the presence of binding protein in acid–ethanol extracts of ovine fetal and adult plasma. We conclude that acid–ethanol extraction can not be used reliably for the removal of IGF-binding proteins, and that only acid gel filtration is a completely safe and valid method.

J. Endocr. (1988) 119, 453–460
Insulin-like growth factor (IGF)-II and insulin, but not IGF-I, are mitogenic for fetal rat adrenal cells in vitro
Authors: van Dijk J. P. , Tanswell A. K. , Challis J. R. G.
Published: December 2008

The agents controlling growth of the fetal adrenal gland are poorly defined. The purpose of the present study was to determine the factors required to promote proliferation of adrenal cells obtained from fetal rats at 20 days of gestation and grown in monolayer cell culture under serum-free conditions. Insulin stimulated [3H] thymidine incorporation into DNA at all concentrations (0·01–10 mg/l) tested. Rat insulin-like growth factor (IGF)-II in the presence of insulin promoted a dose-dependent increase in mitogenic activity, with a half-maximal concentration of approximately 1 μg/l; IGF-II had no effect in the absence of insulin. There was no significant effect of IGF-I on mitogenic activity in the presence or absence of insulin. Adrenal cell DNA synthesis was not stimulated by ACTH, several ACTH-related peptides, a variety of known growth factors, several steroids, or conditioned medium from fetal adrenal cells. We conclude that in the presence of insulin, IGF-II is a specific growth factor for the fetal rat adrenal. We also suggest that rat fetal adrenal cells, in common with other epithelial cell types under serum-free culture conditions, may respond to this progression factor without an obligatory requirement for an initial exposure to competence factors.

J. Endocr. (1988) 119, 509–516
Effect of melatonin on the peripheral concentrations of LH and progesterone after oestrus, and on conception rate in ewes
Authors: Wallace J. M. , Robinson J. J. , Wigzell S. , Aitken R. P.
Published: December 2008

It has previously been shown that administration of the indoleamine melatonin to advance the breeding season of ewes is also associated with an increase in ovulation rate and subsequent litter size.

Experiment 1 assessed whether, in ewes receiving melatonin to advance the breeding season, the indoleamine acts directly on the corpus luteum to enhance progesterone secretion or indirectly through increased activity of the hypothalamic pulse generator. Six ewes received 3 mg melatonin orally at 15.00 h daily from 22 March onwards, six were induced to ovulate during mid-anoestrus following withdrawal of a progestagen pessary and injection of exogenous gonadotrophin and six acted as naturally ovulating controls. First overt oestrus occurred between 17 May and 8 July in melatonin-treated ewes, between 21 October and 3 January in control ewes and on 8 July in all induced ewes. On days 2 and 10 after the first overt oestrus, melatonin-treated ewes had pulsatile LH activity characteristic of that measured in control ewes ovulating naturally during the breeding season. There was an absence of any pulsatile LH activity in the induced ewes. Progesterone concentrations between days 7 and 12 following oestrus were significantly higher in melatonin-treated than in control and induced ewes, suggesting a luteotrophic role for melatonin.

Experiment 2 was carried out to determine whether administration of melatonin commencing after induced ovulation and insemination would alter the endocrine status of the ewe and thereby influence the establishment of pregnancy and embryo survival. Thirty-two anoestrous ewes were induced to ovulate on 29 June. Starting 24 h after intra-uterine insemination, 16 ewes were given melatonin daily for 60 days and 16 acted as controls. Daily LH concentrations were higher in melatonin-treated than in control ewes from days 2 to 22 after oestrus, while prolactin concentrations declined in melatonin-treated ewes over the same period. Plasma progesterone concentrations were enhanced in melatonin-treated ewes between days 4 and 9 following oestrus, yet ovulation rates were the same as for controls. Successful pregnancies occurred in 0·56 control (9 of 16) and 0·69 melatonin-treated (11 of 16) ewes. For these ewes the number of fetuses surviving to term as a proportion of ovulation rate was 0·43 and 0·51 for the control and melatonin treatment respectively.

J. Endocr. (1988) 119, 523–530
Localization of α-interferon in the human feto-placental unit
Authors: Howatson A. G. , Farquharson M. , Meager A. , McNicol A. M. , Foulis A. K.
Published: December 2008

The distribution of α-interferon in human placental tissue was investigated by immunocytochemical study of paraffin wax-embedded tissue sections using a sheep α-interferon antiserum. Fifty-eight placentas of gestational ages from 8 to 40 weeks were examined.

α-Interferon was present in the syncytiotrophoblast of the chorionic villi of all placentas and was also in macrophages in 28 cases. The appearances suggest production of interferon in human placental trophoblast and, in view of its diverse biological effects, support the concept of a role for α-interferon in the complex series of events required for successful gestation.

J. Endocr. (1988) 119, 531–534
Actions of synthetic parathyroid hormone-related protein(1–34) on the isolated rat kidney
Authors: Ebeling P. R. , Adam W. R. , Moseley J. M. , Martin T. J.
Published: December 2008

The isolated perfused rat kidney was used to study the effects of parathyroid hormone-related protein (PTHrP) on renal cyclic AMP (cAMP) and electrolyte excretion. A perfusate of PTHrP(1–34) increased cAMP excretion from 0·14 ± 0·09 (s.e.m.) nmol/l glomerular filtrate (GF) in controls to 24·67 ± 5·14 (P < 0·01) and decreased calcium excretion from 0·278 ± 0·033 to 0·162 ± 0·011 μmol/l GF (P < 0·01). Human PTH(1–34) (0·7 nmol/l) caused no significant change in calcium excretion, whilst the rise in cAMP excretion was similar to that with PTHrP. PTHrP(1–34) (7 nmol/l further increased cAMP production to 366·7 ± 100·8 nmol/l GF (P < 0·01), higher than the rise with hPTH(1–34) (7 nmol/l) which was 76·7 ± 46·8 (P < 0·05). With the higher concentrations of both peptides (7 nmol/l), calcium excretion was further reduced to 0·090 ± 0·009 μmol/l GF (P < 0·01), whilst phosphate excretion increased with both PTHrP and PTH. PTHrP (7 nmol/l) caused a fall in urinary pH compared with controls (P < 0·05). At low and high concentrations of both hormones, urinary pH was lower with PTHrP than hPTH (P < 0·01). Thus PTHrP, like PTH, acts on the kidney to increase cAMP and phosphate excretion and reduce calcium excretion, but PTHrP may be more effective. Disparate effects on urinary pH could be reflected in the clinical features of humoral hypercalcaemia of malignancy.

Journal of Endocrinology (1989) 120, 45–50
Plasma levels of atrial natriuretic peptides during pregnancy and post partum in the rat
Authors: Jansakul C. , King R. G. , Boura A. L. A. , Brennecke S. P. , Handberg G. M.
Published: December 2008

Plasma concentrations of atrial natriuretic peptides (ANP) in female Wistar rats were measured by radioimmunoassay at oestrus, during pregnancy, during parturition and between 3 h and 4 days post partum. Concentrations of ANP in rats on days 10, 15 and 17 of pregnancy were not significantly different from those in non-pregnant animals in oestrus (32·5 ± 2·2 pmol/l; mean ± s.e.m., n = 9), but levels near term (days 20 and 21 of pregnancy) were reduced by approximately 50%. However, plasma concentrations of ANP at 6, 12 and 24 h post partum were approximately twice those of non-pregnant animals in oestrus, but returned to normal levels within 4 days after parturition. Maternal plasma volume increased significantly during pregnancy, and fell 15–20% 6–24 h post partum. These results suggest that the relationship between plasma volume and the plasma concentration of ANP is reset during pregnancy and changes rapidly post partum. The results do not necessarily, however, imply any changes in the relationship between atrial pressure and the concentration of ANP.

Journal of Endocrinology (1989) 120, 113–117
Autoradiographic studies of androgen-binding sites in human benign prostatic hyperplasia in vitro
Authors: Lasnitzki I. , Takeda H. , Mizuno T.
Published: December 2008

Steroid autoradiographic techniques were used to visualize the distribution of androgen receptor-positive cells in human benign prostatic hyperplasia grown in organ culture. The tissue consisted of alveoli embedded in dense fibromuscular stroma and lined either with one row of cuboidal secretory cells or with several layers of epithelial cells. In some explants alveoli were seen lined with spindle-shaped cells. The autoradiographs showed that in most explants both epithelium and stroma contained androgen receptor-positive cells but that the uptake was less pronounced in the stromal cells. In alveoli lined with several cell layers the basal cells seemed to incorporate less androgen than secretory cells on the luminal side. In alveoli lined with spindle-shaped cells, these were always androgen receptor-negative.

Journal of Endocrinology (1989) 120, 167–170
Oestradiol, vasoactive intestinal peptide and fibroblast growth factor in the growth of human pituitary tumour cells in vitro
Authors: Prysor-Jones R. A. , Silverlight J. J. , Jenkins J. S.
Published: December 2008

The growth of two human prolactin-secreting cell lines developed in our laboratory has been investigated in response to a number of factors. Oestrogen stimulated the synthesis of DNA and protein and increased prolactin secretion. Dexamethasone had the opposite effect to oestrogen. In the presence of serum, epidermal growth factor (EGF) inhibited cell growth at concentrations of 5 ng/ml. Known secretagogues of prolactin (vasoactive intestinal peptide (VIP), TRH, bombesin and neurotensin) were investigated for their action on cell growth but only VIP had a stimulatory effect. Two preparations of fibroblast growth factor (FGF) were studied. One form, derived from bovine pituitary glands, stimulated human pituitary cell growth. In contrast, another FGF, of the basic type (rFGF), was inhibitory to cell growth, increasing the time for cell doubling from 30 to 72 h. This inhibitory effect of rFGF was modified but not abolished by serum, oestradiol, platelet-derived growth factor or EGF. We conclude that bovine pituitary contains at least two fibroblast growth factors, both of which stimulate fibroblast cell growth, but one stimulates and the other inhibits human pituitary tumour cell growth.

Journal of Endocrinology (1989) 120, 171–177
Effect of exogenous prolactin and bromocriptine on seasonal reproductive quiescence in the Bennett's wallaby (Macropus rufogriseus rufogriseus)
Authors: Brinklow B. R. , Loudon A. S. I.
Published: December 2008

Two experiments were performed to investigate whether prolactin blocks the reactivation of the corpus luteum during seasonal reproductive quiescence in the Bennett's wallaby. In the first experiment three groups of non-lactating females (groups (A–C) were subjected in mid-April to photoperiods corresponding to those of the summer solstice from day 0 to day 13 of the experiment. Between days 14 and 52, photoperiods were reduced to correspond to those of the winter solstice (groups B and C). Animals in group A were maintained on the long photoperiods. Two milligrams ovine prolactin (groups A and C) or vehicle (group B) were administered on the mornings of days 14–22. In group A, no animal showed evidence of an active corpus luteum based on increased plasma progesterone levels. All animals in groups B and C exhibited reactivation of the corpus luteum. In group C, reactivation was significantly (P < 0·01) delayed by a mean of 6·3 days.

In the second experiment, two groups of non-lactating female wallabies in 'seasonal quiescence' were injected daily for 7 days with either 60 mg of the dopamine agonist bromocriptine or vehicle. The corpora lutea did not reactivate in either group. We conclude that exogenous prolactin is able to block the effect of short photoperiods in reactivating the quiescent corpus luteum during seasonal quiescence. However, the absence of an effect of bromocriptine suggests that if prolactin is the endogenous hormone responsible for maintaining seasonal quiescence it may not be under dopaminergic control at this time of year.

Journal of Endocrinology (1989) 120, 189–193
Steroids in equine testes: the identification of endogenous 19-hydroxy and 19-nor neutral steroids by gas chromatography–mass spectrometry
Authors: Dumasia M. C. , Houghton E. , Jackiw M.
Published: December 2008

After homogenization of testicular tissue from stallions aged 1, 2 and 5 years, the unconjugated and conjugated steroids were isolated by a combined solvent–solid extraction procedure. The conjugates were further separated into glucuronides and sulphates by chromatography using Sephadex LH-20. After enzyme hydrolysis and solvolysis of the respective conjugate classes, the three extracts, unconjugated steroids, aglycones and solvolysed sulphates, were purified by chromatography using Kieselgel 60H columns. Five fractions were resolved from each extract; an aliquot of each fraction was derivatized to form the methoxime-trimethylsilyl ethers and the steroids were identified by combined gas chromatography–mass spectrometry. The results have shown that in stallion testes (1) steroidogenesis proceeds by both the 4-ene and the 5-ene pathways, (2) age-linked changes occur in both unconjugated and sulphoconjugated steroid fractions and (3) 19-hydroxy androgens and the 19-nor (C18) neutral steroids (19-norandrostenedione and 19-nortestosterone) are detected only in the unconjugated fraction whereas oestrone, the isomers of oestradiol and of 5(10)-oestrene-3,17-diol are the only steroids detected in the sulphoconjugate fraction. It is suggested that the unconjugated 19-oxygenated androgens present in stallion testes are converted to 19-nor neutral steroids by a reverse aldol reaction and a mechanism showing the putative intermediates in their formation is illustrated.

Journal of Endocrinology (1989) 120, 223–229
Stabilization, accurate determination, and purification of rat liver nuclear thyroid hormone receptor
Authors: Ichikawa K. , Brtko J. , DeGroot L. J. , Hashizume K. , Yamada T.
Published: December 2008

Rat liver nuclear thyroid hormone receptor lost 3,5,3′-tri-iodo-l-thyronine (T3)-binding activity with a half-life of 14 days, 4 h, 139 min, 62 min, 16 min or 6 min at 0, 36, 38, 40, 43 or 45 °C respectively, when present in crude nuclear extracts. Glycerol increased the half-life of the receptor during heat inactivation. Protection was reversible by removing the glycerol. The receptor was unstable at a pH below 6·0 or above 10·0. We also found a loss of the receptor activity during the separation of bound and free hormone using the resin test. Of several conditions tested for the separation of bound and free hormone, the addition of heated nuclear extract gave the most accurate estimation of bound hormone when using the resin test. Using these characteristics of the receptor, we purified the receptor to 1220 pmol T3-binding capacity/mg protein with a final yield of 14·6 μg/4 kg rat liver.

Journal of Endocrinology (1989) 120, 237–243
Formation of 4-oestrene-3,17-dione (19-norandrostenedione) by porcine granulosa cells in vitro is inhibited by the aromatase inhibitor 4-hydroxyandrostenedione and the cytochrome P-450 inhibitors aminoglutethimide phosphate and ketoconazole
Authors: Khalil M. W. , Morley P. , Glasier M. A. , Armstrong D. T. , Lang T.
Published: December 2008

The origin and biosynthesis of 4-oestrene-3,17-dione (19-norandrostenedione), a major steroid in porcine ovarian follicular fluid, was investigated by culturing granulosa cells from 4–6 mm follicles of prepubertal gilts with radiolabelled androstenedione and 19-hydroxyandrostenedione. Steroid metabolites were purified by solvent extraction and lipophilic column chromatography, and analysed by C18 reverse-phase high-performance liquid chromatography. 19-Hydroxyandrostenedione, 19-norandrostenedione and oestradiol-17β were obtained as major metabolites from androstenedione, while 19-norandrostenedione and oestradiol-17β were the major products from 19-hydroxyandrostenedione. Serum alone or serum plus FSH significantly enhanced formation of 19-norandrostenedione and oestradiol-17β from each substrate, compared with controls.

Micromolar concentrations (1 μmol/l) of 4-hydroxyandrostenedione, an aromatase inhibitor, significantly reduced formation of 19-norandrostenedione and oestradiol-17β by granulosa cells cultured with serum and FSH. Formation of 19-norandrostenedione and oestradiol-17β from androstenedione and 19-hydroxyandrostenedione was also significantly inhibited by aminoglutethimide phosphate, a cytochrome P-450 inhibitor known to block the conversion of androstenedione to oestrogens. Ketoconazole, an inhibitor of the cytochrome P-450 dependent 17,20-lysase, blocked formation of 19-norandrostenedione and oestradiol-17β only at millimolar concentrations. These results suggest that 19-norsteroid and oestrogen formation from C19 aromatizable androgens may share a common or overlapping pathway, and imply that 19-norsteroid and oestrogen synthesis is mediated by cytochrome P-450 dependent enzymes.

Journal of Endocrinology (1989) 120, 251–260
Effect of adrenomedullectomy and propranolol treatment on the response of gonadotrophins to chronic stress in male rats
Authors: Ariznavarreta C. , Calderón M. D. , Tresguerres J. A. F. , López-Calderón A.
Published: December 2008

In order to study the involvement of the adrenal medulla in stress-induced inhibition of gonadotrophin secretion, we measured plasma concentrations of LH, FSH and corticosterone in adult male rats subjected to chronic restraint after surgical ablation of the adrenal medulla. In intact animals, chronic restraint (6 h daily over 4 days) induced a significant (P<0.05) decrease in plasma concentrations of LH, whereas plasma concentrations of corticosterone showed the expected significant (P<0.01) increase. Adrenomedullectomy did not significantly modify basal plasma concentrations of LH or corticosterone. In these rats, there was no significant decrease of LH after stress, while the increase in corticosterone was as significant as in sham-operated animals (P<0.01). In order to confirm the role of adrenomedullary catecholamines in stress-induced gonadotrophin inhibition another group of rats was treated s.c. with the β-adrenergic blocker propranolol (2 mg/kg twice daily). These rats showed an attenuated inhibition of LH during stress similar to that observed in adrenomedullectomized rats. Levels of FSH were significantly reduced after stress in the saline-treated group, while there were no differences between stressed or unstressed rats in the propranolol-treated group. These results may be considered as evidence that medullary catecholamines, acting through β-receptors, are factors involved in gonadotrophin inhibition during chronic stress.

Journal of Endocrinology (1989) 120, 275–279
A dual role of growth hormone as a feminizing and masculinizing factor in the control of sex-specific cytochrome P-450 isozymes in rat liver
Authors: Mode A. , Wiersma-Larsson E. , Ström A. , Zaphiropoulos P. G. , Gustafsson J.-Å.
Published: December 2008

The effects of GH on the major constitutive sex-specific forms of cytochrome P-450 (P-45015β and P-45016α) were studied in hypophysectomized rats at the mRNA level. Time-course experiments were performed with or without simultaneous treatment with thyroxine and cortisol. Intermittent administration of GH, mimicking the male secretory pattern, caused complete masculinization of the male specific P-45016α at a pretranslational level in the absence and presence of thyroxine and cortisol. When GH was administered continuously, mimicking the female secretory pattern, the female specific P-45015β was induced, an effect that was dramatically potentiated by simultaneous treatment with thyroxine and cortisol. A synergistic effect of thyroxine and cortisol at a pretranslational level was demonstrated, although the major potentiating effect could be attributed to thyroxine. Thus it was concluded that GH, depending on its secretory pattern is the sole masculinizing factor for cytochrome P-450, and that it is also a feminizing factor, although this activity requires the synergistic action of thyroid hormones and glucocorticoids to reach its full effect.

Journal of Endocrinology (1989) 120, 311–317
Steroid concentrations in rat corpora lutea isolated during the oestrous cycle and pseudopregnancy: effect of induction of ovulation at dioestrus
Authors: Uilenbroek J. Th. J. , Woutersen P. J. A. , van der Vaart P. D. M.
Published: December 2008

Corpora lutea could be identified under the dissection microscope up to 7 days after formation. They were isolated during the oestrous cycle and pseudopregnancy and the progesterone and 20α-OH-progesterone contents were compared with serum values of these steroids. The pattern of progesterone in serum resembled that found in the corpora lutea. However, the pattern of 20α-OH-progesterone concentrations in serum and corpora lutea were different. While 20α-OH-progesterone concentrations in the corpora lutea showed large variations during the cycle, changes in serum concentrations of 20α-OH-progesterone were relatively small. Measurement of hormone concentrations in isolated corpora lutea is therefore a sensitive method for studying corpus luteum activity.

To study whether corpora lutea derived after ovulation of immature follicles showed deficient luteal activity, rats at dioestrus (2 days before pro-oestrus) were induced to ovulate by the injection of 10 IU human chorionic gonadotrophin (hCG) and subsequent luteal activity was studied by measuring hormone concentrations in the corpora lutea on day 5 of pseudopregnancy. Concentrations of progesterone, but not of 20α-OH-progesterone, in corpora lutea derived from follicles induced to ovulate at dioestrusday 1 were significantly lower than those in corpora lutea derived from follicles induced to ovulate at prooestrus. This difference was observed not only when pseudopregnancy was induced by cervical stimulation but also when it was induced by implantation of a pituitary gland under the kidney capsule. However, in the latter case, corpora lutea already present on the day of hCG injection also became activated.

The present experiments demonstrate that by measuring hormone concentrations in isolated corpora lutea changes in luteal activity can be studied effectively. Moreover, it appears that corpora lutea derived from immature follicles contained less progesterone than those derived from fully mature follicles.

Journal of Endocrinology (1989) 120, 325–330
Insulin-like growth factor-I binding proteins in serum from the domestic fowl
Authors: Armstrong D. G. , McKay C. O. , Morrell D. J. , Goddard C.
Published: December 2008

This investigation describes the presence of insulinlike growth factor-I (IGF-I) binding proteins in chicken serum. Whole blood was collected from broiler chickens of 7–9 weeks of age and analysed for binding proteins after gel permeation chromatography under both neutral and acidic conditions, and by polyacrylamide gel electrophoresis in the presence of 12·5% sodium dodecyl sulphate (SDS-PAGE).

When serum was chromatographed under neutral conditions, about 70% of the IGF-I immunoreactivity was associated with a large protein complex (Mr=150 000) and 20–25% was associated with an intermediate-sized protein complex (Mr = 45 000). Up to 6% of the serum IGF-I immunoreactivity was eluted in a fraction which corresponded to an Mr of about 7500 and was presumably free IGF-I. Chromatography under acidic conditions dissociated the IGF-I/protein complexes and revealed the presence of an acid-stable binding protein (Mr = 50 000–60 000).

After analysis of serum by SDS-PAGE, three monomeric IGF-I binding proteins (Mr = 28 800, 33 200 and 40 700) were detected. The largest monomer (Mr = 40 700) is probably the binding protein component of the intermediate-sized IGF-I/protein complex. The relationship between the other monomers and both the large IGF-I/protein complex and the acid-stable binding protein is not known.

Although the pattern of binding proteins in chicken serum is similar to that observed in mammals, a major difference is the presence of up to 6% of the serum IGF-I immunoreactivity in an unbound form.

Journal of Endocrinology (1989) 120, 373–378
Prenatal androgenization selectively modifies some responses to oestrogen in the prepubertal rat uterus
Authors: Arriaza C. A. , Mena M. A. , Tchernitchin A. N.
Published: December 2008

Exposure of fetuses to some hormonally active agents may imprint permanent changes on the action of related hormones. These changes can be detected in adulthood as a modification of the degree of responsiveness to hormone action. The present study describes the effect of prenatal androgenization on the various responses to oestrogen in different types of cells in the uterus of prepubertal rats. Prenatal androgenization completely abolishes oestrogen-induced hypertrophy of uterine luminal and glandular epithelium, while it does not interfere with hypertrophy of circular myometrium and potentiates uterine eosinophilia and oedema. This dissociation between the various responses to oestrogen suggests that prenatal androgenization does not equally affect all uterine cell types.

Journal of Endocrinology (1989) 120, 379–384
A monoclonal antibody to lactogenic receptors from female rat liver
Authors: Emtner M. , Brandt J. , Johansson U. , Jouper B. , Fryklund L. , Roos P.
Published: December 2008

Affinity-purified lactogenic receptors from female rat liver microsomal membranes were used to raise antibodies in female Balb/c mice. Mouse spleen and myeloma cells were fused and hybridoma-derived monoclonal antibodies (Mabs) were produced by in-vitro cell culture. Mab from a selected clone was sequentially purified by chromatography on a thiophilic gel and on agarose-bound protein A. The Mab was found to be of IgG1 subclass and of κ type.

The Mab recognized membrane-bound and solubilized (by the detergent heptaoxyethylene lauryl ether; G3707) receptors as well as receptors purified by affinity chromatography and subsequent sodium dodecyl sulphate (SDS) electrophoresis from female rat liver. The Mab bound to receptors from several other female rat tissues, such as ovary, kidney and adrenal, whereas there was no binding to liver receptors from cow and rabbit. Displacement experiments showed that the Mab was specific for a lactogenic type of receptor, in agreement with the finding that the Mab did not recognize receptors from male rat liver. The Mab also bound to cytoplasmic receptors (present in the supernatant after centrifugation at 100 000 g) from female rat liver, suggesting a structural similarity between the cytoplasmic and the microsomal receptors.

Analysis of purified receptors by SDS electrophoresis and subsequent Western blot with 125I-labelled Mab as a probe showed one band corresponding to an Mr of 45 500 ± 2500 (n=5). The same band was obtained with 125I-labelled human GH, showing that the Mab binds to the unit which accommodates the hormone-binding site. The binding sites are, however, not identical since the binding of Mab to the receptor did not inhibit the hormone–receptor interaction. Whether this binding unit represents the intact receptor molecule or a part of it cannot be concluded.

Journal of Endocrinology (1989) 120, 401–407
Excitation-secretion coupling: involvement of potassium channels in ACTH-stimulated rat adrenocortical cells
Authors: Gallo-Payet N. , Payet M. D.
Published: December 2008

The mechanism by which ACTH stimulates calcium influx and steroid secretion was studied using rat adrenal glomerulosa cells, which were either freshly isolated or maintained in primary culture for 3 days. The potassium channel blocker tetraethylammonium chloride (TEA) stimulated twofold both corticosterone and aldosterone secretion; this stimulation was lower than that induced by ACTH at low concentrations (10 pmol/l). However, TEA and ACTH induced similar increases in Ca2+ influx and inositol phosphate accumulation. The three responses (steroid secretion, calcium influx and inositol phosphate accumulation) induced by TEA or low concentrations of ACTH were blocked by CoCl2. The greater stimulatory effect on steroid secretion of 10 nmol ACTH/l was decreased but not blocked by CoCl2. These data further document the complex mechanism of action of ACTH. It is postulated that, at low concentrations, ACTH binds preferentially to the high-affinity site of its receptor, leading to calcium influx by depolarization of the membrane potential, and to steroid secretion predominantly through an inositol phosphate- and Ca2+-stimulated pathway and also a cyclic AMP pathway. At higher concentrations, the hormone also binds to the low-affinity site of its receptor, largely stimulating cyclic AMP production and further increasing steroid secretion.

Journal of Endocrinology (1989) 120, 409–421