bluuebunny/crossref_metadata_2025 huggingface dataset:
Prolactin receptor expression in the gastrointestinal tract: characterization of the prolactin receptor of gastric mucosa
Authors: Lobie P. E. , García-Aragón J. , Waters M. J.
Published: December 2008

There is evidence that prolactin (PRL) influences gastrointestinal function. However, the sites at which prolactin exerts these effects are not known. A monoclonal antibody was therefore generated against the rabbit mammary gland prolactin receptor (MAb 218) and used to study the distribution of the prolactin receptor in the rabbit gastrointestinal tract (GIT) by immunohistochemistry. MAb 218 is an IgG 1 κprecipitating antibody which precipitates major affinity cross-linked mammary gland prolactin receptor subunits of molecular masses 45 and 80 kDa. It has an affinity of 0·8 × 109 mol/l for the prolactin receptor and does not react with GH or insulin receptors in precipitation assays. MAb 218 immunoreactivity was observed in classical prolactin target cells such as mammary gland epithelium, and this immunoreactivity was abolished by preincubation of MAb 218 with purified prolactin receptor but not by preincubation with purified GH receptor.

In the GIT, the most intense immunoreactivity was associated with the oesophageal epithelium, chief (zymogenic) cells of the fundic mucosa, pancreatic islets of Langerhans and surface epithelial cells of the duodenum and jejunum. Other specific elements of the GIT were immunoreactive at lower levels or were immunonegative. No immunoreactivity was observed in these locations with a control monoclonal antibody (MAb 50·8) of identical isotype to 218.

To support the immunohistochemical findings, rabbit gastric mucosal membranes were used to show the presence of lactogen-specific binding. Scatchard analysis of 125I-labelled human GH binding to the gastric mucosal membranes with rat prolactin as displacing ligand yielded an affinity constant (Ka) of 1·0 ± 0·2 × 109 mol/l with a capacity of 3·5 ± 0·4 fmol/mg protein. Affinity cross-linking and sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the gastric receptor revealed lactogenic hormone-binding subunits of molecular masses 43, 68 and 83 kDa. The 68 kDa subunit was not seen in rabbit mammary gland or ovarian tissue, and may be unique to gastric mucosa.

In conclusion, we have demonstrated the presence of a high affinity lactogenic receptor in specific epithelial cell subpopulations of the GIT. This localization of the prolactin receptor in the GIT will assist in further functional assignment of prolactin to gastrointestinal physiology.

Journal of Endocrinology (1993) 139, 371–382
The role of nitric oxide derived from l-arginine in the control of steroidogenesis, and perfusion medium flow rate in the isolated perfused rat adrenal gland
Authors: Cameron L. A. , Hinson J. P.
Published: December 2008

The present studies were designed to investigate the role of nitric oxide (NO) in the regulation of adrenocortical function, using the intact rat adrenal gland in situ, perfused with medium (Hank's balanced salt solution) containing a range of concentrations of l-arginine, the substrate for NO production. In addition, the effects of NG-nitro-l-arginine methylester (l-NAME), an inhibitor of NO production, were investigated. Results showed that l-arginine caused a dose-dependent increase in the flow rate of the perfusion medium through the adrenal gland. This effect was specific, as neither d-arginine nor l-lysine had an effect. The presence of l-NAME (5 mmol/l) in perfusion medium containing l-arginine caused a decrease in flow rate to levels seen in the absence of l-arginine. In the presence of concentrations of l-arginine up to 500 μmol/l, corticosterone secretion rates were also stimulated in a dose-dependent manner. Further studies, investigating the effect of l-arginine on the response to ACTH(1–24) stimulation, found that the percentage increase in flow rate, aldosterone secretion and corticosterone secretion caused by ACTH were not significantly different using media containing 230 μmol l-arginine/l or in the absence of l-arginine.

These results suggest a role for NO derived from l-arginine in the regulation of basal levels of adrenal vascular tone in the rat isolated adrenal gland preparation. They do not suggest an obligatory role for NO in either the vascular or steroidogenic response to ACTH stimulation.

Journal of Endocrinology (1993) 139, 415–423
Thyrotrophin-dependent desensitization by Chinese hamster ovary cells that express the recombinant human thyrotrophin receptor
Authors: Haraguchi K. , Peng X. , Kaneshige M. , Anzai E. , Endo T. , Onaya T.
Published: December 2008

To determine whether thyrotrophin (TSH)-induced desensitization requires a thyroid-specific factor(s), the human TSH (hTSH) receptor was expressed in Chinese hamster ovary cells. The first incubation of the cells with TSH decreased the subsequent response of adenosine 3′,5′-cyclic monophosphate to freshly added TSH in the second incubation. This homologous desensitization was observed as early as after 3 h of the first incubation. The lowest dose of TSH that elicited desensitization was 0·1 nmol/l. The desensitization was not overcome by adding higher doses of TSH in the second incubation. A 125I-labelled TSH-binding study revealed a decrease in the number of high-affinity binding sites but not in that of low-affinity binding sites. The data suggest that TSH-induced desensitization in hTSH receptor-transfected cells is caused, at least in part, by a decrease in the number of TSH receptors on the cell surface. The evidence demonstrates, contrary to an earlier report, that a thyroid-specific factor(s) is not required for hTSH receptor desensitization.

Journal of Endocrinology (1993) 139, 425–429
Pharmacokinetic and galactopoietic response to recombinant variants of bovine growth hormone
Authors: Eppard P. J. , White T. C. , Birmingham B. K. , Hintz R. L. , Bentle L. A. , Wood D. C. , Salsgiver W. J. , Rowold E. , Miller M. A. , Ganguli S. , Hale M. D. , Krivi G. G. , Collier R. J. , Lanza G. M.
Published: December 2008

Two studies were designed to examine the pharmacokinetic and galactopoietic potency of three molecular variants of recombinant-derived bovine GH (rbGH): [Met1, Leu127]-bGH, [Ala1, Val127]-bGH and [Ala1, Val127, His133]-bGH. Histidine substitution for arginine at residue 133 of rbGH was shown to impart thrombin resistance. In a Latin square design, nine lactating Holstein cows received a 25 mg rbGH bolus infusion via the jugular vein followed by frequent blood sampling over the next 12 h. The serum GH concentration data were found to fit to a two-compartment open model. Neither primary nor secondary kinetic parameter estimates differed significantly (P>0·05) among the three rbGH variants. Thus, the disposition of GH concentration at time t was described by the equation C(t)=(1295·5 μg/l) (e−(0·11/min)(t)) + (317·3 μg/l)(e−(0·03/min)(t)). Overall averages were: area under the curve=27·1 mg · min per 1, clearance=0·15 litres/min per 100 kg and volume of distribution of the central compartment =2·59 litres/100 kg. The t1/2 for the two compartments averaged 8·2 and 29·1 min. In the second study, 36 lactating Holstein cows received i.m. injections of one of four oil-based formulation treatments: control vehicle or 500 mg of one of the three rbGH variants every 14 days for 42 days. Average and maximum serum GH concentrations and area under the curve estimates were increased by approximately 3–6 μg/l, 5–15 μg/l and 40–90 μg · day per 1 respectively. Ala1, Val127 rbGH treatments elicited greater blood GH concentrations than [Met1, Leu127]-bGH when administered in an oil-based formulation. Blood GH responses did not directly translate into milk response differences, possibly due to differences in biopotency or receptor availability. Thrombin resistance resulting from substitution of histidine at position 127 of rbGH did not affect blood GH pharmacokinetic parameters or milk response over other rbGH variants.

Journal of Endocrinology (1993) 139, 441–450
Role of adenylate cyclase-cyclic AMP-dependent signal transduction in the ACTH-induced biphasic growth effect of rat adrenocortical cells in primary culture
Authors: Arola J. , Heikkilä P. , Voutilainen R. , Kahri A. I.
Published: December 2008

ACTH has a biphasic effect on the proliferation of fetal rat adrenocortical cells in primary culture. Dramatic changes occurred during the first 72 h of ACTH stimulation, when incorporation of bromodeoxyuridine was used as an indicator of proliferation. The primary effect of ACTH was the inhibition of proliferation during the first 24 h, which was followed by an intense stimulatory phase during the third day of ACTH treatment. Cycloheximide (a protein synthesis inhibitor) prevented both the inhibitory and the stimulatory effects of ACTH, but did not affect the basal proliferation of unstimulated zona glomerulosa-like cells. Although adrenocortical cells stimulated with cyclic AMP (cAMP) derivatives, 8-bromo cAMP (8-Br cAMP) or dibutyryl cAMP ((Bu)2cAMP), differentiated morphologically into fasciculata-like cells, and secreted corticosterone and 18-OH-deoxycorticosterone, as did ACTH-stimulated cells, neither of the derivatives inhibited proliferation during the first 24 h of treatment. In contrast to ACTH, (Bu)2cAMP had a stimulatory effect on bromodeoxyuridine incorporation during the first 24 h of treatment. 8-Br cAMP did not change proliferation during the 24 h of treatment, but had a stimulatory effect after 72 h, which was not seen with (Bu)2cAMP.

Thus, these results suggest that (1) differentiation, steroid hormone synthesis and the mitogenic effect of ACTH are transduced through the cAMP-mediated system, (2) the antimitogenic effect of ACTH is transduced via a cAMP-independent pathway and (3) both antimitogenic and mitogenic effects of ACTH are dependent on protein synthesis.

Journal of Endocrinology (1993) 139, 451–461
Maternal vitamin D status has no effect on the ontogeny of calcium-binding proteins in the duodenum, kidney and cerebellum of fetal mice
Authors: Shamley D. R. , Buffenstein R. , Veale G. , Pettifor J. M.
Published: December 2008

The effects of vitamin D3 deficiency on the ontogeny of calcium-binding proteins (CaBPs) and the vitamin D receptor in the duodenum, kidney and cerebellum of the mouse were examined. Maternal vitamin D status did not affect the time of appearance of the fetal 28 kDa CaBP (CaBP-D28k) in the cerebellum, kidney and duodenum, and the 9 kDa CaBP (CaBP-D9k) in the intestine and kidney. Vitamin D receptor was undetectable in all fetal tissues, regardless of maternal vitamin D status, at all stages of gestation examined. Thus it appears that maternal vitamin D status does not affect the ontogeny of CaBP-D9k or CaBP-D28k in the mouse fetus. The factors that influence the appearance of calbindins in the fetus are unclear.

Journal of Endocrinology (1993) 139, 473–478
Testrosterone-induced compared with oestradiol-induced immunosuppression against Plasmodium chabaudi malaria
Authors: Benten W. P. M. , Wunderlich F. , Herrmann R. , Kühn-Velten W. N.
Published: December 2008

Testosterone suppresses immunity against malaria caused by Plasmodium chabaudi in B10 mice. Since this effect is probably not mediated through the classical androgen-receptor response, we investigated whether testosterone might act, after aromatization to oestradiol (OE2), through the oestrogen receptor (ER). Indeed, OE2 was found to act immunosuppressively when used at only about 1% of the immunosuppressive dose of testosterone. This becomes evident as an OE2-induced suppression of self-healing of P. chabaudi infections in female and castrated male B10 mice. The immunosuppressive OE2 effect is associated with a 16-fold increase in the circulating level of OE2 and can be prevented by ER blockers such as tamoxifen and clomifene. In contrast, the immunosuppressive effect of testosterone, which is not associated with any changes in the level of OE2, cannot be abolished by ER blockers or by aromatase inhibitors, such as atamestane and drofazar hydrochloride. Moreover, OE2 and testosterone act differently on spleen cells; OE2 induces a decrease in CD4+-T-cells, whereas testosterone causes an increase in CD8+-T-cells and a decrease in total nucleated spleen cells. The immunosuppressive effect of testosterone, but not that of OE2, can be adoptively transferred to syngeneic mice by nucleated spleen cells, predominantly T-cells. Our data show that the immunosuppressive activity of testosterone, in contrast to OE2, is not mediated through the ER. The immunosuppressive action of testosterone is therefore thought to be primarily mediated through a non-genomic mechanism.

Journal of Endocrinology (1993) 139, 487–494
Immunological activities of highly purified isoforms of human FSH correlate with in vitro bioactivities
Authors: Burgon P. G. , Robertson D. M. , Stanton P. G. , Hearn M. T. W.
Published: December 2008

In a recent study, a five- to eightfold range in human FSH radioreceptor activity (RRA) was documented for highly purified isoforms of FSH when the data were expressed on an FSH protein content basis as determined by amino acid analysis. This study examined the FSH in vitro bioactivity and immunoactivity of these preparations. FSH in vitro biological activity showed a five- to eightfold range in activity with a high correlation with the RRA values (r=0·82). A similar five- to eightfold range of values was obtained with a specific FSH radioimmunoassay and an FSH two-site immunoassay with high correlations again observed between each other, between each immunoassay and with either the in vitro bioassay or the RRA method (r=0·77–0·995). Although there was overall a close correlation between these assays, significant differences in ratios of activities between the in vitro bioassay and other methods were observed with highly purified FSH isoform preparations from different pI regions.

The high correlation between in vitro bioassay/RRA methods and immunoassay methods over a wide range of isoform specific activities suggests that these methods are detecting similar structural features on each isoform. It is thus concluded that these immunoassays are not solely measuring hormone mass based entirely on amino acid composition. This conclusion raises questions about ratio measurements of FSH, where immunoassay methods are presumed to measure total protein content, and their application in physiological situations and clinical practice.

Journal of Endocrinology (1993) 139, 511–518
Effects of insulin-like growth factor-I peptides in rats with acute renal failure
Authors: Martin A A , Gillespie C M , Moore L , Ballard F J , Read L C
Published: December 2008

The effect of insulin-like growth factor-I (IGF-I) administration on body weight gain and the rate of recovery of renal function was investigated in rats following an acute episode of renal ischaemia. Since the des(1–3)IGF-I and LR3IGF-I variant forms of IGF-I have been shown to be more potent than IGF-I, their effects were also examined. Acute renal failure was produced in male Sprague–Dawley rats by clamping both renal arteries for 45 min. Treatment was commenced at the time of renal artery occlusion with vehicle (0·1 mol acetic acid/l; control group), IGF-I (2·0 mg/kg per day), des(1–3)IGF-I (2·0 mg/kg per day) or LR3IGF-I (1·5 mg/kg per day) by s.c. osmotic pump, and continued for 7 days, with rats being held in metabolism cages. Glomerular filtration rate (GFR) was estimated by the use of 51Cr-EDTA continuously infused i.p. via osmotic pump. Following the episode of renal ischaemia, body weight gain and nitrogen retention were significantly improved in all three peptide-treated groups, and serum urea concentrations were reduced in the groups treated with IGF-I and des(1–3)IGF-I. However, there was no evidence of the variants having any increased potency over the growth effects of IGF-I itself. GFR was significantly reduced, urine output was increased and urinary concentrating ability was reduced in all groups compared with normal rats, with no significant effect of the IGF peptides being apparent.

A closer examination of the acute effects of LR3IGF-I on renal function was undertaken by measuring GFR for 3 days before and 3 days after renal ischaemia in two groups of rats, treated for the latter 3 days with either vehicle (controls) or LR3IGF-I (1·5 mg/kg per day). LR3IGF-I treatment following renal ischaemia resulted in a significantly greater fall in GFR than in controls, urinary osmolality was also significantly reduced, and fractional excretion of sodium was increased. In addition, there was histological evidence of a greater degree of tubular epithelial calcification in the kidneys of the rats treated with LR3IGF-I.

This study showed that administration of IGF peptides at doses sufficient to cause significant improvement in anabolic status did not improve renal function in rats following an acute episode of renal ischaemia. Indeed the LR3IGF-I variant of IGF-I had a deleterious effect on renal function in the early stage of the recovery period.

Journal of Endocrinology (1994) 140, 23–32
The role of neuropeptides in the regulation of adrenal zona glomerulosa function: effects of substance P, neuropeptide Y, neurotensin, Met-enkephalin, Leu-enkephalin and corticotrophin-releasing hormone on aldosterone secretion in the intact perfused rat adrenal
Authors: Hinson J P , Cameron L A , Purbrick A , Kapas S
Published: December 2008

A range of neuropeptides has been identified in the adrenal glands of many mammalian species. In many cases these peptides have been located in nerves supplying the adrenal cortical cells, or within clusters of chromaffin cells within the zona glomerulosa. The function of these neuropeptides has yet to be determined, but from their location within the gland it is clearly possible that they may have a role in the regulation of aldosterone secretion. The effects of Met-enkephalin, Leu-enkephalin, neuropeptide Y, substance P, corticotrophin-releasing hormone (CRH) and neurotensin on aldosterone secretion were investigated using the intact perfused rat adrenal gland in situ. All the peptides tested, except CRH, caused a significant increase in aldosterone secretion over the dose range of 1 pmol to lOnmol, with a maximum response of about a twofold increase in secretion. Met-enkephalin, however, at a dose of 10 nmol caused a 350% increase in aldosterone secretion, a response comparable with that seen in response to angiotensin II in this preparation. These results suggest that, while substance P, neuropeptide Y, neurotensin and Leu-enkephalin all have the capacity to cause modest increases in the rate of steroid secretion by the zona glomerulosa, these neuropeptides probably do not have a major role in the acute regulation of aldosterone secretion, at least under basal conditions. Met-enkephalin, on the other hand, was a more potent stimulus to aldosterone secretion, and thus may have a role in the control of aldosterone secretion.

Journal of Endocrinology (1994) 140, 91–96
FSH and LH up-regulate epidermal growth factor receptors in rat granulosa cells
Authors: Fujinaga H , Yamoto M , Shikone T , Nakano R
Published: December 2008

Epidermal growth factor (EGF) modulates ovarian folliculogenesis and steroidogenesis and its binding sites have been demonstrated in the ovary. We investigated the localization of EGF-binding sites in the rat ovary, and the effects of FSH and LH on EGF binding to cultured granulosa cells. Autoradiographic localization of 125I-labelled mouse EGF-binding sites was demonstrated in the granulosa and luteal cells. Displacement study and Scatchard analysis showed that a single class of specific binding sites for 125I-labelled mouse EGF was present in the granulosa cells, obtained from the ovaries of immature rats treated with diethylstilboesterol. The number of binding sites and the apparent dissociation constant were 4336 binding sites/cell and 3·42 pmol/l respectively. The granulosa cells were cultured for 48 h at 37 °C in medium alone or with increasing amounts of ovine FSH (oFSH; 1–1000 μg/l). FSH treatment increased 125I-labelled mouse EGF binding to the granulosa cells in a dose-dependent manner. After culture with oFSH (100 μg/l) for 48 h, the cells were cultured in medium alone or with increasing amounts of ovine LH (oLH; 1–1000 μg/l) for an additional 48 h. LH treatment also increased 125I-labelled mouse EGF binding in a dose-dependent manner, compared with the control. However, neither FSH nor LH altered receptor-binding affinity. Furthermore, after culture with oFSH (FSH-primed) or oFSH followed by oLH (LH-primed), tissue plasminogen activator (tPA) activities in the conditioned media were examined by fibrin autography. FSH-primed or LH-primed granulosa cells were more responsive to EGF action to induce an increase in tPA activity. In conclusion, it is suggested that functional receptors for EGF in rat granulosa cells are up-regulated by FSH and LH.

Journal of Endocrinology (1994) 140, 171–177
In situ localization of muscle insulin-like growth factor-II mRNA in developing bovine fetuses
Authors: Listrat A , Gerrard D E , Boulle N , Groyer A , Robelin J
Published: December 2008

Insulin-like growth factor-II (IGF-II) modulates myogenesis in muscle cell cultures, in utero. IGF-II gene expression is developmentally regulated in several tissues including muscle. Determining whether IGF-II is expressed by developing muscle cells or by neighbouring cells in developing muscle tissue is crucial for determining whether IGF-II exerts a paracrine or an autocrine affect on myogenesis. Semitendinosus muscle samples from 12 bovine fetuses ranging from 60 to 274 days post conception (pc) were analysed for the amount and localization of muscle IGF-II mRNA using Northern, dot blot and in situ hybridization analyses. Northern blot analysis revealed multiple IGF-II transcripts of 5·1, 3·7, 2·6, 2·0, 1·7 and 1·1 kb in developing bovine muscle tissue. The relative amount of muscle IGF-II mRNA increased (P<0·05) until 162 days pc, then decreased (P<0·01) to near undetectable levels by the end of gestation (approximately 284 days pc). Between 60 and 162 days pc, in situ hybridization revealed that the majority of the IGF-II transcripts were localized to developing muscle cells rather than connective tissue. After 162 days pc the IGF-II hybridization signal shifted away from muscle cells and greater accumulation was observed in the connective tissue at 274 days pc. These data confirm that the expression of IGF-II in developing bovine muscle tissue is primarily localized in muscle cells and support the claim that IGF-II acts as an autocrineacting growth factor during myogenesis in vivo.

Journal of Endocrinology (1994) 140, 179–187
Growth hormone but not gonadal steroids influence lipoprotein lipase and hepatic lipase activity in hypophysectomized rats
Authors: Vikman-Adolfsson K , Oscarsson J , Nilsson-Ehle P , Edén S
Published: December 2008

Lipoprotein lipase and hepatic lipase are involved in the degradation and cellular uptake of lipids in peripheral tissues and the liver. These enzymes seem to be influenced by gonadal steroids in the rat as well as in man. Since gonadal steroids have been shown to influence the secretory pattern of GH and since the effect of gonadal steroids on several metabolic functions may be dependent upon their effects on GH secretion, the present study was undertaken to investigate the developmental regulation of heparin-releasable lipoprotein lipase and hepatic lipase activities in female and male rats, and to study the effects of gonadal steroids and different modes of GH administration to hypophysectomized rats on these enzyme activities. Female and male Sprague–Dawley rats from 20 to 65 days of age were studied. Hypophysectomy was performed at 50 days of age and these rats were given replacement therapy with thyroxine and cortisone. Groups of hypophysectomized rats were treated with either oestradiol valerate (0·1 mg/kg per day) or testosterone enanthate (1 mg/kg per day). Bovine GH (1 mg/kg per day) was given to groups of hypophysectomized rats either by two daily subcutaneous injections or by continuous infusion using osmotic minipumps. Hormone treatment was given for 1 week. Lipoprotein lipase and hepatic lipase activities were measured in heparinized plasma.

There was no difference in lipoprotein lipase activity between male and female rats at 20 to 45 days of age. Lipoprotein lipase activity decreased between 45 and 65 days of age in male rats but not in females and, at 65 days of age, lipoprotein lipase activity was higher in females compared with males. Hepatic lipase activity increased from 20 to 45 days of age in both female and male rats but at 45 and 65 days of age it was higher in female than in male rats. Hypophysectomy decreased lipoprotein lipase and hepatic lipase activity in female rats. Neither oestradiol nor testosterone treatment had any effects in hypophysectomized rats. Treatment with bovine GH increased both lipoprotein lipase and hepatic lipase activities irrespective of its mode of administration and these effects were not influenced by additional treatment with oestradiol or testosterone. After the last injection of GH, lipoprotein lipase activity was increased for 12 h. Hepatic lipase activity was increased at 2 and 4 h after the last GH injection but after 12 h the activity had decreased, indicating that the time-course for the effects of GH on lipoprotein lipase and hepatic lipase may be different.

It is concluded that GH markedly influences post-heparin lipoprotein lipase and hepatic lipase activities. The lack of effects of gonadal steroids on these activities in hypophysectomized rats suggests that the gonadal steroids influence these lipases via their influence on GH release.

Journal of Endocrinology (1994) 140, 203–209
Effect of thyroidectomy, and thyroxine and α2u-globulin replacement therapy on testicular steroidogenic and gametogenic activities in rats
Authors: Biswas N M , Ghosh P K , Biswas R , Ghosh D
Published: December 2008

Adult male rats were thyroidectomized and killed after 22 days of treatment. Thyroidectomy lowered the weights of testes and accessory sex organs, decreased the activities of testicular Δ5-3β- and 17β-hydroxysteroid dehydrogenases (HSD), and diminished spermatogenesis, serum levels of testosterone and α2u-globulin. Supplementation with thyroxine at a dose of 5 μg/100 g body weight per day for 21 days or supplementation with α2u-globulin at a dose of 1·5 mg/rat per day for 21 days in thyroidectomized animals partially reversed the decrease in HSD activities and serum concentrations of testosterone and α2u-globulin, while spermatogenesis was restored to normal. The weights of testes and accessory sex organs were also reinstated after supplementation with thyroxine or α2u-globulin in thyroidectomized rats in comparison with thyroidectomized animals. It was concluded that α2u-globulin may be an intermediary in the thyroid hormone control of testicular function.

Journal of Endocrinology (1994) 140, 343–347
Developmental changes in and hormonal modulation of epidermal growth factor concentration in the rat submandibular gland
Authors: Hiramatsu M , Kashimata M , Takayama F , Minami N
Published: December 2008

Developmental changes in and hormonal effects on the concentration of epidermal growth factor (EGF) in the rat submandibular gland were investigated. The level of EGF in the gland gradually increased with age from 4 up to 8 weeks of age; thereafter it increased markedly, reaching a plateau level at 12 weeks of age in both male and female rats. A significant sex difference in EGF levels was observed between 8 and 14 weeks, the level in the males being approximately twice as high as that in the females at 12 and 14 weeks of age. Castration of male rats decreased EGF to about the same level as that of control females. Treatment of castrated rats with testosterone propionate (TP) restored EGF to the levels in control male rats. Ovariectomy and/or administration of oestradiol-17β to ovariectomized rats had no apparent effect on EGF concentration. These findings indicate that the sex difference in EGF concentration can be attributed to the level of endogenous androgens. In addition, hypophysectomy of male rats caused a remarkable decrease in submandibular gland EGF to about 7% of the normal level. This reduction was significantly, although not completely, restored by the administration of TP, tri-iodothyronine (T3) or GH. Moreover, giving TP with T3 or with GH or both together had additive effects on the increase in EGF levels in hypophysectomized rats. These results provide evidence that EGF in the submandibular gland is regulated multi-hormonally by at least TP, T3 and GH.

Journal of Endocrinology (1994) 140, 357–363
Plasma concentration of atrial natriuretic peptide and brain natriuretic peptide during normal human pregnancy and the postpartum period
Authors: Yoshimura T , Yoshimura M , Yasue H , Ito M , Okamura H , Mukoyama M , Nakao K
Published: December 2008

Increases in blood volume are observed during normal gestation and these are reversed shortly after delivery. Although both atrial (A-type) natriuretic peptide (ANP) and brain (B-type) natriuretic peptide (BNP) have been described, the role of these peptides in pregnancy and the postpartum period are unclear. This study was designed to examine the effects of pregnancy, labour and delivery on plasma levels of ANP and BNP. Plasma levels of ANP and BNP were determined during normal pregnancy, 30 min after separation of the placenta (immediately postpartum) and between 5 and 72 h postpartum (late postpartum; puerperium). Since the assay sensitivity was 20 pg/ml plasma (for both ANP and BNP), values less than this were assigned a value of 20 pg/ml to calculate means. Plasma levels of ANP and BNP were significantly higher at term pregnancy than during the first trimester (ANP increased from 20 ± 0·2 to 57 ± 10 pg/ml (s.e.m.), P<0·001; BNP increased from 25 ± 2 to 49 ± 9 pg/ml, P<0·01). The plasma level of ANP then rose to 157 ± 38 pg/ml 30 min after separation of the placenta, being significantly (P<0·01) higher than that seen at term pregnancy. It declined significantly (P<0·001) to 32 ± 3 pg/ml in the late postpartum period. In contrast, the plasma level of BNP 30 min after separation of the placenta was 80 ± 25 pg/ml, and increased to 116 ± 17 pg/ml in the late postpartum period, significantly (P<0·01) higher than the level at term pregnancy. We conclude that ANP and BNP may play a role in controlling blood volume during normal human pregnancy at term and during transition to the postpartum period. Changes in ANP immediately postpartum and BNP in the later postpartum period appear to be differentially regulated.

Journal of Endocrinology (1994) 140, 393–397
Inhibition of growth hormone bioactivity by recombinant human growth hormone-binding protein in the eluted stain assay system
Authors: Dattani M T , Hindmarsh P C , Brook C G D , Robinson I C A F , Marshall N J
Published: December 2008

The effects of a recombinant human GH-binding protein (rhGHBP; amino acids 1–238) on GH stimulation of rat Nb2 lymphoma cells were examined with an eluted stain assay system (ESTA). This precise bioassay utilizes the colorimetric reduction by stimulated Nb2 cells of a yellow tetrazolium salt (3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) to a purple formazan as its end-point. The use of a lactogenic bioassay allowed the investigation of hGHBP specificity for human GH (hGH) as opposed to prolactin. rhGHBP inhibited pituitary hGH bioactivity in a dose-dependent manner. No significant inhibition of prolactin or ACTH bioactivity occurred. It was confirmed that recombinant 20 kDa hGH also stimulated the Nb2 cells and that its relative potency was ∼ 10% of that of pituitary-derived hGH. Stimulation by 20 kDa hGH was also inhibited by rhGHBP. The highly quantitative ESTA system demonstrated that the binding protein inhibited in a competitive manner. hGH activation of the Nb2 cells did not appear to be governed by a Michaelian first-order reaction. As might then be anticipated, the concentration of rhGHBP required for 50% inhibition of GH bioactivity (IC50) changed with agonist concentrations for both 20 kDa and 22 kDa hGH. However, with equimolar concentrations of these two isohormones, the IC50 of the binding protein was virtually identical. Potentiation of hGH bioactivity in vivo by low concentrations of hGHBP has been reported but was not observed in our in vitro system when tested over a wide range of binding protein concentrations.

In conclusion, the ESTA bioassay system permitted a detailed characterization of the inhibition of hGH bioactivity by rhGHBP. The hormonal specificity confirms earlier radioligand binding studies, except that we found that the 20 kDa hGH variant interacts with the rhGHBP.

Journal of Endocrinology (1994) 140, 445–453
Effect of chronic exposure to a gonadotrophin-releasing hormone agonist on in vitro responsiveness of ovine pituitary cells to inhibin, activin and oestradiol
Authors: Muttukrishna S , Knight P G
Published: December 2008

To investigate the extent to which the direct actions of inhibin, activin and oestradiol on pituitary output of FSH and LH are dependent on the presence of functional gonadotrophin-releasing hormone (GnRH) receptors, we have compared the effects of these agents on cultured ovine pituitary cells derived from control and GnRH agonist-suppressed ewes.

Chronic treatment with GnRH agonist reduced plasma LH and FSH levels (P<0·01) and abolished GnRH-induced release of LH and FSH both in vivo and in vitro. As expected, basal LH release and LH cell content in vitro were drastically reduced in GnRH agonist-suppressed cells (P<0·001). However, basal FSH release and FSH cell content were approximately twofold higher than in control cells (P<0·001).

Irrespective of whether the cells had been desensitized to GnRH, inhibin and oestradiol were both found to suppress basal FSH release and FSH cell content in a dose-dependent fashion (P<0·001). Although inhibin had no effect on basal release of LH from control cells, it markedly enhanced GnRH-induced release (P<0·001). In contrast, inhibin increased (P<0·001) basal LH release from GnRH agonist-suppressed cells (which were unresponsive to the GnRH challenge). Inhibin had no overall effect on total LH content/well for either control or GnRH agonist-suppressed cells. Treatment with oestradiol, on the other hand, reduced total LH content/well, an effect which was more pronounced with GnRH agonist-suppressed cells (−44%; P<0·001) than with control cells (−14%, P<0·01). Whereas in control cells activin had no significant effect on any aspect of FSH production examined, in GnRH agonist-treated cells activin enhanced basal FSH release, residual cell content and total FSH content/well (P<0·001). Altering GnRH receptor status also modified the LH response to activin. With control cells activin increased basal release (P<0·001), decreased GnRH-induced release (P<0·001) and increased total LH content/well (P<0·001). With GnRH agonist-treated cells, however, activin had a uniform inhibitory effect on each aspect of LH production examined (P<0·001 in each case).

It was concluded that desensitization of ovine gonadotrophs to GnRH by chronic agonist treatment results in a paradoxical enhancement of FSH output in vitro but has little effect on the responsiveness of the cells (in terms of gonadotrophin release and content) to either inhibin or oestradiol. In contrast, GnRH agonist treatment leads to qualitative changes in cellular reponsiveness to activin.

Journal of Endocrinology (1994) 140, 483–493
Evidence for a role of phospholipase A2 in the mechanism of LHRH priming in rat anterior pituitary tissue
Authors: Thomson F J , Johnson M S , Mitchell R , Wolbers B
Published: December 2008

The phospholipase A2 (PLA2) inhibitors, quinacrine, p-bromophenacyl bromide, ONO-RS-082, aristolochic acid and chloracysine blocked the priming effect of LHRH, but not acute LHRH-induced gonadotrophin release measured in anterior pituitary pieces in pro-oestrous rats in vitro. These results suggest that the intracellular mechanisms underlying LHRH priming are distinct from those which mediate LH release in the present circumstances in that they involve PLA2. Furthermore, neither LHRH-induced LH release from preprimed tissue nor Ca2+-induced LH release were attenuated by quinacrine, indicating that this inhibitor does not interfere with the general Ca2+-dependent secretory apparatus of the gonadotroph and that the critical period for its action is in the induction of priming. LHRH induced the release of [3H]arachidonic acid ([3H]AA) from [3H]AA-prelabelled anterior pituitary tissue from pro-oestrous rats; a response which was sensitive to inhibitors of PLA2, of protein kinase C (PKC) and of protein synthesis. Activation of PKC also resulted in [3H]AA release which was inhibited with exactly the same pharmacological profile as the response to LHRH. Both gonadotrophin secretion and [3H]AA release responses to LHRH and to phorbol ester varied in parallel during the oestrous cycle and in ovariectomized/oestradiol-17β-replaced animals, as did their sensitivity to quinacrine and the protein synthesis inhibitor cycloheximide. These results indicate that LHRH priming is dependent on a hormonally regulated cascade involving a distinct form of PKC acting through a protein synthesis-dependent step to release AA by means of PLA2 activity. The priming effect was mimicked (at least in part) by conditioning preincubation with AA, confirming the functional relevance of this signalling cascade. Results using standard inhibitors of lipoxygenase/epoxygenase pathways were equivocal as to whether these pathways were critically involved, whilst cyclo-oxygenase inhibitors were completely without effect. The steps downstream from AA (and its possible metabolites) by which stimulus–secretion coupling is up-regulated in priming remain to be clarified.

Journal of Endocrinology (1994) 141, 15–31
Enhanced expression of transforming growth factor-β1 during thyroid hyperplasia in rats
Authors: Logan A , Smith C , Becks G P , Gonzalez A M , Phillips I D , Hill D J
Published: December 2008

Transforming growth factor-β1 (TGF-β1) has been reported to influence the growth rate and iodine uptake and organification in vitro by isolated thyrocytes. We have determined changes in the expression and presence of TGF-β1 within the rat thyroid during goitre induction, and subsequent involution following goitrogen withdrawal. Hyperplastic goitres were induced in adult rats by administration of methimazole together with a low iodine diet for up to 12 weeks. Goitrogen-treated rats quickly became hypothyroid compared with controls, and exhibited thyroid hyperplasia and hypertrophy assessed by thyroid weight, and DNA and protein content (control: total serum thyroxine (T4) 66 ± 4 nmol/l, thyroid weight 5 ± 1 mg/100 g body weight, mean ± s.d., n = 10; 2 weeks goitrogen: T4 undetectable, thyroid weight 27 ± 4 mg/100 g, n = 10). Thyroid growth rate slowed subsequently between 2 and 10 weeks. Messenger RNA for TGF-β1 was compared in the thyroids and livers of control and goitrous rats by ribonuclease protection assay. Low levels of mRNA for TGF-β1 were detected in thyroids from control rats at all time-points, while TGF-β1 mRNA was barely detectable in liver. Thyroid TGF-β1 mRNA levels substantially and progressively increased at 1 and 2 weeks of goitrogen treatment respectively, and remained above control levels at 4 and 10 weeks. As thyroid involution occurred 4 weeks following goitrogen withdrawal, so thyroid TGF-β1 mRNA levels declined. In control animals, the cellular localization of TGF-β1 mRNA, determined by in situ hybridization, was found to be a subpopulation of follicular epithelial cells, and immunohistochemical co-localization of TGF-β1 and calcitonin identified these tentatively as parafollicular or C-cells. During goitre formation, abundant TGF-β1 mRNA and peptide were found to be widely distributed within the entire follicular epithelium. While this ubiquitous distribution had largely disappeared in the involuting gland, TGF-β1 peptide was retained within the parafollicular cells, which appeared more abundant than in thyroids from control animals. These results suggest that an increased local expression of TGF-β1, a putative growth inhibitor, during thyroid hyperplasia may contribute to the temporal stabilization of goitre size.

Journal of Endocrinology (1994) 141, 45–57
The effect of vasopressin and oxytocin on glomerular filtration rate in the conscious rat: contribution to the natriuretic response
Authors: Forsling M L , Judah J M , Windle R J
Published: December 2008

Urine flow, sodium excretion, mean arterial blood pressure and glomerular filtration rate (GFR) were detennined in the conscious unrestrained rat infused with hypotonic saline. The effects of vasopressin infused at 24 and 160 pmol/min and oxytocin infused at 30 and 200 pmol/min were determined. The lower doses of each hormone gave plasma concentrations within the physiological range whereas the higher doses produced plasma concentrations equivalent to those seen following dehydration.

Vasopressin produced dose-dependent antidiuretic and natriuretic responses. Hormone infused at both rates increased the clearance of sodium, but only the higher dose caused a significant increase in GFR. Fractional excretion of sodium was significantly elevated by both doses. Oxytocin produced dose-dependent diuretic and natriuretic responses. Again both rates of infusion increased the clearance of sodium, but only the higher dose caused a significant increase in GFR. The lower dose caused a significant increase in the fractional excretion of sodium.

It appears, therefore, that increases in GFR may have a role in the natriuretic response to both hormones. However, this response can also be seen when GFR remains unchanged. This fact, together with the observed increases in the fractional excretion of sodium, indicates that these hormones have additional tubular actions.

Journal of Endocrinology (1994) 141, 59–67
The induction of hepatic somatotrophic receptors after birth in sheep is dependent on parturition-associated mechanisms
Authors: Breier B H , Ambler G R , Sauerwein H , Surus A , Gluckman P D
Published: December 2008

While the GH receptor (GHR) plays a key role during adult life, its role during fetal development is not well understood. Recent data suggest that GHRs are present in ovine fetal hepatic tissue at mid-gestation. However, the levels of GHR expression are markedly lower in fetal hepatic tissue in comparison with postnatal values. The present study investigates whether the neonatal induction of the hepatic GHR and plasma levels of IGF-I follow a pattern of strictly age-related development or whether birth-associated processes stimulate this increase.

Stereotaxic electrolytic lesioning of the fetal paraventricular nuclei was employed to prolong gestation markedly. We compared the hepatic binding of ovine placental lactogen (oPL) and oGH and plasma levels of IGF-I in these post-mature fetuses with those in pre-term fetuses, pregnant mothers and lambs which were of the same conceptional age as the post-mature fetuses. While specific binding of both 125I-labelled oGH and 125I-labelled oPL to hepatic microsomal membranes was fully reversible in all groups, the specific binding of 125I-labelled oGH was significantly (P<0·001) lower than specific binding of 125I-labelled oPL in all groups of animals. There was no difference in specific I-labelled oGH or 125I-labelled oPL binding in livers or plasma levels of IGF-I in post-mature fetuses in comparison with pre-term fetuses. In contrast, a major increase (P<0·001) in 125I-labelled oGH and 125I-labelled oPL binding and plasma IGF-I levels was observed in lambs. In pregnant females, specific 125I-labelled oGH and 125I-labelled oPL binding and plasma IGF-I levels were significantly (P<0·01) higher compared with the two fetal groups. A significant (P<0·001) correlation was observed between specific binding with 125I-labelled oGH and 125I-labelled oPL (r=0·95, intercept=4·5, slope=2·36). Detailed competitive binding studies showed that the potency of unlabelled oPL in competing with 125I-labelled oPL or 125I-labelled oGH was consistently higher in comparison with unlabelled oGH. The differences in cross-reactivity of oPL and oGH at the distinct developmental stages were related to the differences in affinity between the two ligands and major developmental increases in capacity.

The present study shows major parallel induction of oPL and oGH binding to hepatic microsomal membranes and plasma IGF-I concentrations after birth. The postnatal increase in the hepatic GHR is inhibited if delivery is prevented by stereotaxic destruction of the fetal paraventricular nuclei. Our observation that oGH and oPL binding is co-ordinately induced after birth in hepatic tissue supports the emerging evidence that the two ligands may bind to the same membrane receptor or to related protein(s).

Journal of Endocrinology (1994) 141, 101–108
Opioid peptide and α-adrenoceptor pathways in the regulation of the pituitary-adrenal axis in man
Authors: Delitala G , Trainer P J , Oliva O , Fanciulli G , Grossman A B
Published: December 2008

Opioid peptides are well established as potent inhibitors of the pituitary-adrenal axis, while α1-adrenoceptor drugs have recently been shown to stimulate this axis: both classes of agents appear to work principally above the level of the pituitary, most probable directly on the hypothalamus. There is also evidence that these drugs interact in their control of pituitary-adrenal function, although the specific hypothalamic releasing hormone involved has remained unclear. We have therefore carried out a study into the interaction of methoxamine, an α1-adrenoceptor agonist and naloxone, an opioid antagonist, together with human corticotrophin-releasing hormone (CRH), in a group of healthy volunteers in order to establish the mode of action of these drugs.

The following drugs were administered to a group of seven healthy male subjects in a randomized double-blind manner: methoxamine (6 μg/kg per min over 3 h); naloxone (10 mg bolus); human CRH (100 pg bolus); methoxamine plus CRH; naloxone plus CRH; methoxamine plus naloxone; saline (control). Plasma ACTH and serum cortisol were measured at intervals in each subject, and blood pressure and pulse rate recorded with each sample.

Both CRH and naloxone produce a marked rise in ACTH and cortisol, peaking at approximately 45 min after infusion. In combination, the drugs produced a peak response in plasma ACTH at the same time, but its magnitude was greater than that after either drug alone. Methoxamine produced a rise in plasma ACTH which was maximal at approximately 75 min, as well as a peak rise in serum cortisol at 120 min. This was greater than after either CRH or naloxone alone but, in combination, both drugs produced peak responses not significantly greater than when methoxamine alone was given.

While the interaction of drugs with differing pharmacokinetic profiles renders interpretation difficult, our data suggest that naloxone increases pituitary-adrenal activity via a mechanism independent of CRH, most probably hypothalamic vasopressin. This, albeit indirect, evidence suggests that α1-adrenoceptor activation with methoxamine activates hypothalamic pathways involving both endogenous CRH and vasopressin.

Journal of Endocrinology (1994) 141, 163–168