bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversal of long-term LH deprivation on testosterone secretion and Leydig cell volume, number and proliferation in adult rats
Authors: Keeney D. S. , Sprando R. L. , Robaire B. , Zirkin B. R. , Ewing L. L.
Published: December 2008

The purpose of this study was to determine whether Leydig cell volume and function could recover fully from long-term LH deprivation upon restoration of endogenous LH secretion, and whether the restoration of LH would elicit a mitogenic response, i.e. stimulate Leydig cell proliferation or affect Leydig cell number per testis. LH secretion was inhibited by treating adult rats with testosterone and oestradiol-filled (TO) silicone elastomer implants (16 weeks), and was restored by removing the implants. Changes in serum concentrations of LH and FSH, LH-stimulated testosterone secretion by testes perfused in vitro, Leydig cell volume and number per testis, average Leydig cell volume and Leydig cell [3H]thymidine incorporation were measured at weekly intervals following implant removal.

The TO implants inhibited (P < 0·01) LH secretion, but serum concentrations of FSH were not significantly different (P > 0·10) from control values. After implant removal, serum LH returned to control values within 1 week, whereas serum FSH increased twofold (P < 0·01) and returned to control values at 4 weeks. LH-stimulated in-vitro testosterone secretion was inhibited by more than 99% in TO-implanted rats, but increased (P < 0·01) to 80% of control values by 8 weeks after implant removal. The total volume of Leydig cells per testis and the volume of an average Leydig cell were 14 and 19% of control values respectively, after 16 weeks of TO implantation (P < 0·01), but returned to 83 and 86% of controls (P > 0·10) respectively, by 6 weeks after implant removal.

Leydig cell proliferation ([3H]thymidine labelling index) was low (< 0·1%) in both control and TO-implanted rats, increased (P < 0·01) fivefold from 1 to 4 weeks after implant removal and then declined to control values at 6 weeks. The increase in Leydig cell [3H]thymidine incorporation was mimicked by treating TO-implanted rats with exogenous LH, but not FSH.

Leydig cells were identified in both the interstitium and the lamina propria of the seminiferous epithelium. The proportion of Leydig cell nuclei in the lamina propria was 30-fold greater (P < 0·01) at 1 and 3 weeks after implant removal (3%) compared with that for control and TO-implanted rats (0·1%). Total Leydig cell number per testis was marginally but not significantly (P = 0·06) decreased in rats treated with TO implants for 16 weeks when compared with controls (18·4±2·2 vs 25·4±1·2 × 106). Three weeks after implant removal, the numbers of Leydig cells per testis were identical (26·8±2·8 × 106) to those in control animals. These results not only demonstrate dramatic morphogenic effects of LH on mature rat Leydig cells, but also suggest that endogenous LH might be mitogenic at least to a subpopulation of Leydig cells.

Journal of Endocrinology (1990) 127,47–58
Effects of crude and highly purified bovine inhibin (Mr 32 000 form) on gonadotrophin production by ovine pituitary cells in vitro: inhibin enhances gonadotrophin-releasing hormone-induced release of LH
Authors: Muttukrishna S. , Knight P. G.
Published: December 2008

Primary cultures of ovine pituitary cells (from adult ewes) were used to investigate the actions of steroid-free bovine follicular fluid (bFF) and highly-purified Mr 32 000 bovine inhibin on basal and gonadotrophin-releasing hormone (GnRH)-induced release of FSH and LH. Residual cellular contents of each hormone were also determined allowing total gonadotrophin content/well to be calculated.

As in rats, both crude and highly purified inhibin preparations promoted a dose (P < 0·001)- and time (P < 0·001)-dependent suppression of basal and GnRH-induced release of FSH as well as an inhibition of FSH synthesis, reflected by a fall in total FSH content/well. However, while neither inhibin preparation affected basal release of LH or total LH content/well, GnRH-induced LH release was significantly (P< 0·001) increased by the presence of either bFF (+ 75%) or highly-purified inhibin (+ 64%) in a dose- and time-dependent manner. This unexpected action of bFF on GnRH-induced LH release was abolished in the presence of 5 μl specific anti-inhibin serum, confirming that the response was indeed mediated by inhibin. Furthermore, neither oestradiol-17β (1 pmol/l–10 nmol/l) nor monomeric α-subunit of bovine inhibin (2·5–40 ng/ml) significantly affected basal or GnRH-induced release of LH.

These in-vitro findings for the ewe lend support to a number of recent in-vivo observations and indicate that, in addition to its well-documented suppressive effect on the synthesis and secretion of FSH, inhibin may actually facilitate LH release in this species, in marked contrast to its action in the rat.

Journal of Endocrinology (1990) 127, 149–159
Importance of the concentration of ATP in rat pancreatic β cells in the mechanism of streptozotocin-induced cytotoxicity
Authors: Nukatsuka M. , Yoshimura Y. , Nishida M. , Kawada J.
Published: December 2008

The effects of streptozotocin (STZ) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) on monolayer cultures of rat pancreatic β cells were compared. The intracellular NAD concentration was markedly decreased by both 2 mmol STZ/l and 13·6 μmol MNNG/l, but insulin secretion was decreased significantly only by STZ. The intracellular ATP level decreased rapidly and in a time-dependent manner with STZ, but decreased less on treatment with MNNG: 80% decrease with STZ but only 35% decrease with MNNG in 12 h in the cells exposed to the chemicals for 1 h and then washed thoroughly. STZ decreased oxygen consumption of rat liver mitochondria in a time- and dose-dependent manner and enhanced the generation of hydroxyl radicals (DMPO-adducts). This enhancement was doubled on the addition of succinate as a substrate. Mitochondrial ATP production was also decreased significantly by STZ, but not by MNNG. Thus the marked depletion of intracellular ATP in β cells by STZ seems to be due mainly to a direct effect on mitochondrial production. From these results, we suggest that the cytotoxic effect of STZ in pancreatic β cells is due to a reduction in the intracellular level of ATP, rather than of NAD.

Journal of Endocrinology (1990) 127, 161–165
Analysis of the ratio of biological to immunological LH secreted during the oestrogen-induced LH surge in the ewe
Authors: Clarke I. J. , Foulds L. M. , Hayward S. , Cummins J. T. , Robertson D. M.
Published: December 2008

Plasma concentrations of in-vitro biological and immunological LH were measured throughout the LH surge in cyclic ewes and in ovariectomized ewes treated i.m. with oestradiol benzoate. Both activities increased in parallel during the LH surge in both groups, although the ratio of biological to immunological activities (B/I ratio) was highest at the peak of the LH surge. The two activities were highly correlated (r = 0·86–0·92), with similar slopes from their regression analysis for the cyclic and ovariectomized groups (1·15 and 1·16 respectively). However, the intercepts of the regression lines did not pass through the origin, but intersected the y (radio-immunoassay) axis, suggesting that these serum samples contained immunoactivity not associated with LH bioactivity. In conclusion, an increase in the LH B/I ratio was observed during the LH surge in oestrogen-treated ovariectomized ewes and in cyclic ewes. This increase was not attributable to a change in the relationship between these two LH activities during the LH surge, but rather to the detection of bioinactive immunoactive material in plasma of unknown composition.

Journal of Endocrinology (1990) 127, 217–222
Ovarian secretion rates and peripheral concentrations of inhibin in normal and androstenedione-immune ewes with an autotransplanted ovary
Authors: Campbell B. K. , Baird D. T. , McNeilly A. S. , Scaramuzzi R. J.
Published: December 2008

Active immunization of sheep against androstenedione results in an increase in ovulation rate that is associated with increased plasma levels of LH and progesterone, but not FSH. Although immunized ewes have more activated follicles the secretion rate of oestradiol is not increased. An experiment was conducted to examine the effect of androstenedione immunity on the ovarian secretion and peripheral plasma concentrations of inhibin.

Merino ewes in which the left ovary had been autotransplanted to a site in the neck were divided into control (n = 5) and androstenedione-immune (n = 6) groups. Ovarian and jugular venous blood was collected every 10 min at two stages of the follicular phase, 21–27 h and 38–42 h after a luteolytic dose of an analogue of prostaglandin F2α (PG), and every 15 min for 6 h on day 10 of the subsequent luteal phase. The ewes were monitored regularly for luteal function by measurement of the concentration of progesterone and preovulatory LH surges. The concentration of inhibin in jugular and ovarian venous plasma was determined by radioimmunoassay and ovarian secretion rates and peripheral concentrations are expressed as pg of 1–26 peptide fragment of the α chain.

The ovarian secretion rate of inhibin tended to be greater in androstenedione-immune ewes at all stages of the oestrous cycle measured, with this difference being statistically significant (P <0·05) during the luteal phase (100±40 and 260±80 (s.e.m.) pg/min for control and immune groups respectively). The pattern of ovarian inhibin secretion exhibited pulsatile-like fluctuations which were not associated with LH pulses. Peripheral concentrations of inhibin were generally higher in immunized than in control ewes with this difference being significant (P < 0·01) from day 4 to 14 of the luteal phase (59±5 and 110±7 ng/1 for control and immune respectively). The ovarian secretion rate of immunoactive inhibin was greater (P <0·01) during the follicular phase than during the luteal phase in both groups of ewes, and peripheral concentrations of inhibin increased (P < 0·001) following injection of PG in ewes from both treatment groups.

We concluded that androstenedione immunity results in an increase in ovarian inhibin secretion, an effect that can probably be attributed to the greater number of large oestrogenic follicles present in the ovaries of these ewes. Furthermore, this increase in the concentration of inhibin may override any decrease in the negative feedback effects of ovarian steroid produced by immunization and, hence, explain the paradoxical findings of normal concentrations of FSH and raised concentrations of LH in ewes which are immunized against androstenedione.

Journal of Endocrinology (1990) 127, 285–296
Ontogeny of gonadotrophin receptors and gonadotrophin-stimulated cyclic AMP production in the neonatal rat ovary
Authors: Sokka T. , Huhtaniemi I.
Published: December 2008

The sequence of appearance of FSH and LH receptors, and response of cyclic AMP (cAMP) production to these hormones and cholera toxin, were studied in the fetal and neonatal rat ovary. Specific binding of radio-labelled human (h)FSH and chorionic gonadotrophin (CG) to ovarian homogenates was first detectable on day 7 of life. The content of FSH receptors per ovary increased tenfold between days 7 and 16, and that of LH receptors 27-fold. A significant response of cAMP production in vitro to FSH appeared on day 4 of life, but no significant effect of hCG on cAMP was achieved until day 7. In contrast, cholera toxin had a marked effect on cAMP production by day 17 of fetal life. Although both FSH and LH receptors were detectable in the neonatal rat ovary by day 7, the present findings indicate that the FSH responsiveness of the ovary appears earlier than that of LH. The post-receptor machinery of cAMP production is already functional in the fetal ovary as shown by the experiments with cholera toxin. The appearance of the receptor may therefore be the last link in the ontogeny of the gonadotrophin signal transduction system in the ovary. To study the hormone dependence of the appearance of gonadotrophin responsiveness, neonatal female rats were treated on days 1–6 or 1–9 of life with a potent gonadotrophin-releasing hormone antagonist, and killed on the following day. In both treatment groups, the pituitary LH and FSH contents were suppressed. The body weights remained unaltered, but ovarian weights decreased significantly during both periods of treatment (days 1–6,26·1%, P < 0·05; days 1–9,54·0%, P <0·001). No difference in basal or FSH-stimulated cAMP production was achieved by antagonist treatment for the first 6 days of life. The basal and hCG-stimulated rates of cAMP production per ovary were reduced in animals treated for 9 days (P <0·01), but the FSH-stimulated cAMP production remained unaffected. Hence, whereas the responsiveness to FSH seems to develop in the absence of normal gonadotrophin secretion, a causal relationship between normal gonadotrophin levels and the appearance of LH/hCG responsiveness is apparent in the neonatal rat ovary.

Journal of Endocrinology (1990) 127, 297–303
Cytoplasmic pH in the action of insulin-like growth factor-I in cultured porcine thyroid cells
Authors: Takasu N. , Komiya I. , Nagasawa Y. , Asawa T. , Shimizu Y. , Yamada T.
Published: December 2008

The effects of insulin-like growth factor-I (IGF-I) on cytoplasmic pH (pHi) and [3H]thymidine incorporation were studied in primary cultures of porcine thyroid cells. IGF-I alkalinized thyroid cells and stimulated thymidine incorporation in a dose-dependent manner; the effects of IGF-I on alkalinization (the maximal rates of change of cytoplasmic pHi/min ((dpHi/dt)max)) and thymidine incorporation were observed at 2 ng/ml and were maximal at 100 ng/ml, with half-maximal stimulation at approximately 10 ng/ml. The results indicate that Na+/H+ exchange or cell alkalinization may function as a transmembrane signal transducer in the action of IGF-I on thyroid cell proliferation. Several mitogens and comitogens which activate sodium hydrogen exchange, including epidermal growth factor, platelet-derived growth factor and nerve growth factor, have been listed. Activation with IGF-I has not, however, been presented before. Thus the present study constitutes the first demonstration of IGF-I-stimulated activation of Na+/H+ exchange or cell alkalinization.

Journal of Endocrinology (1990) 127, 305–309
Effect of gastrin-releasing peptide on the secretion of mouse islet hormones in vitro
Authors: Wilkes L. C. , Bailey C. J. , Thompson M. G. , Conlon J. M. , Buchanan K. D.
Published: December 2008

Collagenase-isolated mouse islets were incubated with gastrin-releasing peptide (GRP). At 5·6 mmol glucose/1, 10 nmol GRP/l increased the release of insulin (by 50%) and glucagon (by twofold), decreased the release of pancreatic polypeptide (by 35%), but did not significantly affect the release of somatostatin. At 16·7 mmol glucose/l, 10 nmol GRP/l increased glucagon release (by fivefold) and decreased pancreatic polypeptide release (by 46%), without significantly altering insulin and somatostatin release. GRP (200 nmol/l) did not affect insulin release by perifused mouse islets at 2·8 mmol glucose/l, but increased both first and second phase insulin release after a square wave increase in the glucose concentration to 11·1 mmol/l. At 5·6 mmol glucose/l, GRP (100 pmol/1–100 nmol/l) increased (by 50–70%) insulin release by the RINm5F clonal cell line. GRP did not affect glucose oxidation or the cyclic adenosine monophosphate content of RINm5F cells. However, the intracellular free Ca2+ concentration of RINm5F cells was rapidly and transiently increased by GRP (maximum increase of 64% about 10 s after exposure to 1 μmol GRP/l). The rise of intracellular free Ca2+ was approximately halved in the absence of extracellular Ca2+. The results suggest that GRP may contribute to the normal regulation of the endocrine pancreas. The insulin-releasing effect of GRP is mediated via increased cytosolic free Ca2+, derived both from an increased net influx of extracellular Ca2+ and from mobilization of intracellular Ca2+ stores.

Journal of Endocrinology (1990) 127, 335–340
Characterization of insulin-like growth factor-binding proteins in rat serum, lymph, cerebrospinal and amniotic fluids, and in media conditioned by liver, bone and muscle cells
Authors: Gargosky S. E. , Walton P. E. , Wallace J. C. , Ballard F. J.
Published: December 2008

Insulin-like growth factor-binding proteins (IGFBPs) in rat serum, lymph, amniotic fluid and cerebrospinal fluid (CSF), and in rat cell-conditioned media were characterized using a combination of gel-permeation chromatography, Western immunoblots and Westernligand analysis. Adult serum and abdominal lymph contained a 200 kDa IGFBP (the putative type-II IGF receptor) and a 150 kDa IGFBP that contained subunits of 40–50 kDa aligning with porcine IGFBP-3 on Western-ligand blots. In addition, both fluids contained the smaller IGFBPs: a 30 kDa IGFBP which was immunoreactive with IGFBP-2 antiserum, a 28 kDa IGFBP which electrophoresed with human IGFBP-1, and a 24 kDa IGFBP. In contrast, fetal serum and amniotic fluid lacked the 150 kDa and the 28 kDa IGFBPs. CSF contained only a 30 kDa IGFBP, but this was not IGFBP-2. Several IGFBPs were detected in media conditioned by liver, bone and muscle cells. Liver-derived cells and some hepatoma cell lines produced similar patterns upon ligand blot analysis, i.e. IGFBPs of 30 kDa (which reacted with IGFBP-2 antiserum), 28 kDa and 24 kDa. A hepatoma cell line, HTC, and a smooth muscle cell line contained only an IGFBP of 26 kDa. Skeletal muscle-derived cells (L6 myoblasts) produced a 28 kDa, a 26 kDa and a 24 kDa IGFBP. Both calvarial osteoblasts and osteogenic sarcoma cells produced an IGFBP of 30 kDa that cross-reacted with IGFBP-2 antisera. In addition, osteogenic sarcoma cells produced a 28 kDa and a 24 kDa IGFBP. These results allow us partially to classify and to compare the IGFBPs in rat fluids and those produced by cultured cells.

Journal of Endocrinology (1990) 127, 391–400
Enhanced potency of truncated insulin-like growth factor-I (des(1–3)IGF-I) relative to IGF-I in lit/lit mice
Authors: Gillespie C. , Read L. C. , Bagley C. J. , Ballard F. J.
Published: December 2008

The relative potencies of insulin-like growth factor (IGF-I) and the N-terminal truncated derivative, des(1–3)IGF-I, have been compared in lit/lit mice. Injection of 30 μg IGF-I, 30 μg des(1–3)IGF-I or 3 μg des(1–3)IGF-I daily for 3 weeks increased total length and nose-rump length of the animals substantially more than in controls or animals treated with 3 μg IGF-I daily.

Body weight changes were not statistically significant. The lower dose of des(1–3)IGF-I, but not that of IGF-I, led to increases in kidney and heart weights relative to controls, while the higher dose of either IGF-I or des(1–3)IGF-I also increased the weights of liver, lungs and stomach. These results indicate that the higher potency of des(1–3)IGF-I demonstrated in cultured cells also applies in vivo to at least one strain of GH-deficient animals.

Journal of Endocrinology (1990) 127, 401–405
Homologous and heterologous regulation of somatostatin-binding sites on chicken adenohypophysial membranes
Authors: Harvey S. , Baidwan J. S. , Attardo D.
Published: December 2008

Binding of 125I-labelled [Tyr1]-somatostatin (125I-[Tyr1]-SRIF) to pituitary caudal lobe membranes was suppressed in immature chickens 1 and 2 h after i.v. administration of unlabelled SRIF at concentrations of 1–100 μg/kg. In-vitro preincubation of chicken pituitary glands for 0·5–4·0 h with 0·1 μmol SRIF/l similarly reduced the binding of 125I-[Tyr1]-SRIF to caudal lobe membrane preparations. After a 4-h incubation in 0·1 mmol SRIF/l, the withdrawal of SRIF from the incubation media was accompanied 4 h later by a partial recovery in the binding of 125I-[Tyr1]-SRIF to pituitary membranes. Passive immunoneutralization of endogenous SRIF resulted in a prompt (within 1 h) and sustained (for at least 24 h) suppression of 125I-[Tyr1]-SRIF binding to pituitary membranes. The i.m. administration of cysteamine (300 mg/kg) to 12-week-old birds depleted hypothalamic SRIF stores and decreased the density of 125I-[Tyr1]-SRIF-binding sites in the caudal and cephalic lobes of the chicken pituitary gland. The reduction in SRIF content and in SRIF-binding sites occurred within 1 h of cysteamine administration and was maintained for at least 24 h. In 6-week-old birds, cysteamine (300 mg/kg) administration suppressed pituitary binding of 125I-[Tyr1]-SRIF for at least 5 days. Circulati concentrations of GH were markedly decreased 1 and 4 h after cysteamine injection, but not after 24 h.

Pituitary binding sites for 125I-[Tyr1]-SRIF were not affected by pretreatment of pituitary glands for 2–12 h in vitro with thyroxine or oestradiol-17β (1 nmol/l–10 μmol/l) or with ovine GH or recombinant DNA-derived chicken GH (1–100 μg/ml in vitro and 100–1000 μg/kg in vivo). Ovine prolactin, at concentrations of 1–100 μg/ml was also without effect on 125I-[Tyr1]-SRIF binding to pituitary membranes following a 2- or 4-h incubation with pituitary glands. Pituitary binding sites for 125I-[Tyr1]-SRIF were, however, increased after a 24-h incubation with 1 μmol tri-iodothyronine (T3)/l in vitro and 4 and 24 h after the administration of T3 (100–1000 μg/kg) in vivo. Although T3 had no direct inhibitory effect on 125I-[Tyr1]-SRIF binding to pituitary membranes, binding was suppressed 1 and 2 h after the in-vivo administration of T3 at concentrations of 100–1000 μg/kg.

These results therefore demonstrate homologous and heterologous regulation of SRIF-binding sites in the chicken pituitary gland.

Journal of Endocrinology (1990) 127, 417–425
Steroid fatty acid esters in adrenals and plasma: effects of ACTH
Authors: Bélanger B. , Caron S. , Bélanger A. , Dupont A.
Published: December 2008

The presence and production of 5-ene-steroid fatty acid esters (SFA) has been previously reported in bovine adrenals. A study was conducted, using a series of chromatographic procedures and radioimmunoassays, to determine the levels of SFA in adrenals from man, cattle, dog, rat and guinea-pig, and to assess, in both rats and guinea-pigs, the effect of ACTH on SFA production by adrenals and their subsequent secretion into the circulation. The effects of ACTH on plasma SFA and non-conjugated steroid levels were also investigated in human subjects. Our data indicated that adrenal pregnenolone fatty acid ester (PREG-FA) levels were below 40% of PREG levels in cattle, dog, rat and guinea-pig while, in man, PREG-FA levels were threefold those of PREG. A large proportion of dehydroepiandrosterone (DHEA) and 5-androstene-3β,17β-diol were present as fatty acid ester derivatives in the adrenals of all species, with the exception of cattle. In both rats and guineapigs, administration of ACTH caused a sharp increase in adrenal PREG of approximately threefold which lasted for 6 h, while the concentration of adrenal PREG-FA was slightly increased for a short time. In plasma, however, a marked rise in PREG-FA occurred, while the changes in PREG levels were much lower than those of its acylated counterpart. In man, PREG and DHEA concentrations were rapidly stimulated two-fold in the first 30 min following the administration of ACTH, while PREG-FA and DHEA-FA levels were increased by approximately 2·5-fold (P<0·01) at 120 and 180 min. Our data suggest that there is a rapid turnover of SFA in adrenals which causes accumulation of non-polar steroids in the plasma.

Journal of Endocrinology (1990) 127, 505–511
Thyrotrophin-releasing hormone-induced growth hormone (GH) secretion in anaesthetized chickens: inhibition by GH-releasing factor at central sites
Authors: Ahene C. A. , Lea R. W. , Harvey S.
Published: December 2008

Intracerebroventricular (i.c.v.) administration of GH-releasing factor (GRF) (at 1 or 10 μg) to anaesthetized immature (6- to 8-weeks-old) or adult (> 24-weeks-old) domestic fowl had no effect on basal GH concentrations in peripheral plasma, but suppressed (after 20 min) the acute GH response to exogenous (i.v.) thyrotrophin-releasing hormone (TRH) (1 μg/kg). The i.c.v. injection of GRF also reduced the content of somatostatin (SRIF) and dopamine (DA) in the hypothalamus, while increasing the concentration of the DA metabolite 3,4-dihydroxyphenyl acetic acid (DOPAC) and the DOPAC/DA ratio. The release of SRIF from hypothalamic tissue was stimulated in vitro by 100 nmol GRF/l. The inhibitory effect of i.c.v. GRF on TRH-induced GH secretion was blocked when it was simultaneously injected i.c.v. with SRIF antiserum.

These results demonstrate central effects of GRF on avian hypothalamic function and suggest an inhibitory role for this peptide in GH regulation, possibly mediated through increased SRIF secretion.

Journal of Endocrinology (1991) 128, 13–19
Long-term iodination of thyroglobulin by porcine thyroid cells cultured in porous-bottomed culture chambers: regulation by thyrotrophin
Authors: Gruffat D. , Gonzalvez S. , Chambard M. , Mauchamp J. , Chabaud O.
Published: December 2008

Thyroid cells cultured as monolayers on the porous bottom of culture chambers have been shown to express some specific functions of thyroid follicles. This system, which allows independent access to apical and basal media, is suitable for the long-term study of polarized processes, as the cells maintain their polarized organization. Iodination of thyroglobulin has been investigated under different culture conditions in the presence or absence of TSH. Apical thyroglobulin accumulation, apical iodide concentration and thyroglobulin iodination have been followed simultaneously. Iodide (0·5 μmol/l) was added to basal medium at various stages: only once for 4-day incubations and at each medium change or daily for longer experiments. TSH increased the amount of thyroglobulin secreted into the apical medium by five- to sixfold, whereas high basal iodide concentrations (> 5 μmol/l) inhibited thyroglobulin secretion by TSH-stimulated cells. TSH increased iodide uptake giving an iodide concentration ratio between apical and basal media of about 5. Thyroglobulin iodination was dependent upon TSH. Thyroglobulin was iodinated only in the apical compartment. Secretion and iodination of thyroglobulin were polarized phenomena, but the polarity of iodination was total whereas the polarity of secretion was only partial (10% basal secretion). This functional asymmetry was maintained for up to 29 days. The maximal incorporation of iodine into thyroglobulin obtained was never higher than 3·5 atoms/mol. Apical iodide concentrations from 1 to 15 μmol/l, depending on culture conditions, did not increase this value. These results suggest that cells cultured in this culture system are able to reproduce several steps of thyroidal iodide metabolism although there may be unknown factors which could interfere and reduce the efficiency of thyroglobulin iodination.

Journal of Endocrinology (1991) 128, 51–61
Effects of exogenous porcine growth hormone on serum insulin-like growth factor-binding proteins in growing pigs
Authors: Coleman M. E. , Etherton T. D.
Published: December 2008

The insulin-like growth factor-binding proteins (IGFBPs) in sera of growing pigs were partially characterized with respect to their size, immunological relationships to other known IGFBPs and their regulation by porcine (p) GH. Castrated male pigs (14–16 weeks of age) were treated with either vehicle or pGH (up to 100 μg/kg body weight per day) by daily i.m. injection for 7 days. Blood samples were collected by jugular venepuncture at the time of injection. Five IGFBPs of 43, 40, 34, 30 and 26 kDa were identified on ligand blots of porcine sera. A 30 kDa IGFBP, in addition to the 43 and 40 kDa IGFBPs, was immunoprecipitated by antiserum to pIGFBP-3 and found to contain N-linked carbohydrate suggesting that it is a fragment of pIGFBP-3 as has been noted for a 29 kDa N-glycosylated IGFBP in rat sera. The 34 kDa IGFBP in pig sera was precipitated by antisera to rat IGFBP-2 and contained no N-linked carbohydrate. Administration of pGH to normal growing pigs not only increased pIGFBP-3 levels but elicited a dose-dependent suppression of levels of the 34 kDa IGFBP as well. In summary, the Mr pattern of IGFBPs in the sera of growing pigs is similar to that observed in fetal and maternal pig sera and in other species. Furthermore, we report that administration of pGH to normal pigs suppresses the expression of an IGFBP-2-like IGFBP in pig sera while increasing expression of pIGFBP-3.

Journal of Endocrinology (1991) 128, 175–180
Pheromaxein, the pheromonal steroid-binding protein, is a major protein synthesized in porcine submaxillary salivary glands
Authors: Booth W. D. , von Glos K. I.
Published: December 2008

Submaxillary salivary gland tissue from large White, Göttingen miniature and Meishan (Chinese) breeds of pig, and European wild boars, was incubated with [35S]methionine. The radiolabelled amino acid was incorporated into protein in all incubations as demonstrated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Specifically [35S]methionine was predominantly incorporated into the α- and β-charge isomers of pheromaxein, a 16-androstene steroid-binding protein, as shown by SDS-PAGE in combination with vertical isoelectric focusing on polyacrylamide slab gels. The synthesis of pheromaxein occurred in submaxillary gland tissue from both sexes, including tissues stored frozen at −70 °C for long periods. There was little evidence for pheromaxein synthesis in parotid gland tissue or skeletal muscle. Total protein, pheromaxein and total 16-androstenes were determined in the submaxillary gland cytosols of six mature Göttingen miniature boars and a positive correlation was found between these glandular constituents. The amounts of endogenous pheromaxein relative to total protein in the submaxillary gland cytosols (range 10·3–18·0%), together with the predominant synthesis of this protein in vitro, indicate that pheromaxein is a major protein produced in porcine submaxillary glands, particularly in those of the male.

Journal of Endocrinology (1991) 128, 205–212
Thyroidal iodine metabolism in obese-strain chickens before immune-mediated damage
Authors: Sundick R. S. , Herdegen D. , Brown T. R. , Dhar A. , Bagchi N.
Published: December 2008

Several studies have shown that iodine plays a role in spontaneous autoimmune thyroiditis in man and other animals. In addition, abnormalities of iodine metabolism have been found in patients with Hashimoto's thyroiditis and in chickens of the obese strain (OS), an animal model of spontaneous autoimmune thyroiditis. We have examined several parameters of iodine metabolism before immune damage in this model and in the related Cornell strain (CS), a strain which develops a late-onset mild thyroiditis, to discover a possible causal relationship between altered iodine metabolism and the initiation of autoimmunity.

Thyroglobulin was purified from individual chicken thyroid glands and analysed for iodine by the ceric sulphate method. Analogous to the thyroglobulin of Hashimoto's patients, the iodine content of OS thyroglobulin (27 atoms/molecule) was lower than that of normal-strain thyroglobulin (46 atoms/molecule) when the chickens were provided with a normal diet. Also, under conditions of TSH suppression, the iodine content of OS thyroglobulin (18 atoms/molecule) was lower than that of CS thyroglobulin (36 atoms/molecule) and of normal-strain thyroglobulin (32 atoms/molecule). In contrast with Hashimoto's patients, however, the OS and CS chickens had practically no inorganic iodide in their thyroid glands; electrophoretic analysis of thyroid homogenates revealed that essentially all (> 99·62%) 125I was organified by 16 h in all strains of birds tested. Despite the relatively poor iodination of thyroglobulin exhibited by OS chickens, they did not iodinate additional 'unique' proteins, when examined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of thyroid proteins labelled with 125I in vivo.

The release of 125I in vivo under conditions of TSH suppression was examined in chicks receiving thyroxine and propylthiouracil. After 14 days both OS and CS chicks showed poorly suppressible release of 85% and 92% respectively, while the normal strain released 33 %. To determine whether the autonomous function of OS and CS thyroid glands was present in a restricted number of follicles or cells or whether it occurred in a majority of cells, autoradiograms of thyroid glands labelled in vivo from TSH-suppressed chickens were examined. Silver grains were present in all cells, indicating that autonomous function was a characteristic of all cells.

These thyroid gland abnormalities are compared with those found in Hashimoto's patients and discussed in the context of their aetiological significance.

Journal of Endocrinology (1991) 128, 239–244
Increased nuclear tri-iodothyronine binding and thyroid hormone-stimulated glucose consumption in mononuclear blood cells from patients with liver cirrhosis
Authors: Kvetny J. , Matzen L.
Published: December 2008

Nuclear tri-iodothyronine (T3) maximal binding capacity (MBC) and thyroxine- and T3-stimulated cellular oxygen consumption and glucose consumption were examined in mononuclear blood cells from six patients with liver cirrhosis (LC), in six patients with alcoholic hepatitis (AH), and in six healthy control subjects.

Serum T3 was decreased in patients with LC. The MBC of T3 was increased significantly (P < 0·05) in cells from patients with LC compared with patients with AH and controls, whereas the equilibrium association constants did not differ. Unstimulated glucose consumption was slightly increased (P < 0·05) in cells from patients with AH and LC compared with controls. Thyroid hormone-stimulated glucose consumption was significantly (P < 0·05) increased in cells from patients with LC compared with controls and patients with AH.

Unstimulated oxygen consumption did not differ between the groups, but thyroid hormone-stimulated oxygen consumption was depressed in cells from patients with AC (P < 0·05) compared with patients with LC and with controls.

We conclude that both thyroid hormone-stimulated glucose consumption and T3 nuclear receptor binding in cells from patients with LC are increased, and suggest that the observed changes are responsible for maintenance of euthyroidism in the face of reduced circulating T3.

Journal of Endocrinology (1991) 128, 321–325
The galactopoietic effect of bovine growth hormone in goats is associated with increased concentrations of insulin-like growth factor-I in milk and mammary tissue
Authors: Prosser C. G. , Royle C. , Fleet I. R. , Mepham T. B.
Published: December 2008

Lactating goats exhibiting widely divergent responses to short-term (4 days) treatment with bovine GH (bGH) were retrospectively divided into two groups based on the magnitude of this response. There was no difference between groups in terms of the pretreatment milk yield, but by day 4 of treatment milk secretion had increased by 4·99±2·5 (s.e.m.) ml/h (P > 0·05 compared with pretreatment) for group 1 and 22·9±2·4 ml/h (P< 0·001) for group 2. Plasma GH increased in both groups, but concentrations were significantly higher both before and during treatment in group 1 compared with group 2. Plasma concentrations of insulin-like growth factor-I (IGF-I) increased significantly during bGH treatment for both groups and there was no significant difference between the two until day 4 of treatment when levels of IGF-I in group 1 began to decline, whereas those from group 2 were maintained. Concentrations of IGF-I in milk from goats in group 1 were not significantly altered by GH administration, whereas those in goats in group 2 were increased by 40% (P < 0·01 compared with pretreatment). Levels of IGF-I in mammary secretory tissue from four animals from group 1 were not altered by bGH (2·8±0·2 and 2·77 ±0·08 nmol/kg tissue before and after treatment respectively), but were significantly (P < 0·05) increased in four animals from group 2 (2·80±0·2 and 9·9±1·1 nmol/kg tissue). Thus, it appears that the galactopoietic response in goats was associated with significantly lower levels of GH in plasma after 3 days of treatment and, more strikingly, greater amounts of IGF-I in milk and mammary tissue. This latter observation is consistent with the hypothesis that the effects of bGH on the mammary gland itself are mediated by IGF-I and that the availability of IGF-I to mammary tissue is an important component of the overall galactopoietic response to bGH.

Journal of Endocrinology (1991) 128, 457–463
[125I]Iodomelatonin-binding sites in the pigeon brain: binding characteristics, regional distribution and diurnal variation
Authors: Yuan H. , Pang S. F.
Published: December 2008

The binding and pharmacological characteristics of melatonin-binding sites labelled by [125I]iodomelatonin in membrane preparations from the pigeon brain were determined. Specific binding of [125I]iodomelatonin in the membrane preparations of pigeon brain was rapid, stable, saturable and reversible. The [125I]iodomelatonin-binding sites had the following order of pharmacological affinities: melatonin > 6-chloromelatonin > N-acetylserotonin > > 5-hydroxytryptamine > tryptamine > 5 -methoxytryptophol, > 1 - acetylin dole-3-carboxytryptamine, 5-hydroxyindole-3-acetic acid, l-tryptophan and 3-acetylindole. Compounds known to act on serotonin receptors, adrenoceptors or cholinoceptors were inactive compared with melatonin. Of the various brain regions studied, melatonin binding was greatest in the hypothalamus, intermediate in the mid-brain, pons-medulla and telencephalon, and low in the cerebellum. Subcellular fraction studies indicated that 39% of the binding was located in the mitochondrial fraction, 34% in the nuclear fraction, 21% in the microsomal fraction and 5·6% in the cytosol fraction. Scatchard analysis of the membrane preparations revealed a dissociation constant (Kd) of 206·3±57·9 pmol/l and a total number of binding sites (Bmax) of 26·7±1·9 fmol/mg protein in the middle of the light period (mid-light). In addition, saturation studies demonstrated that [125I]iodomelatonin-binding sites in pigeon brain membrane preparations were 36·2% higher at mid-light (26·7±1·9 fmol/mg protein) than in the middle of the dark period (19·6±1·25 fmol/mg protein), with no significant variation in their binding affinities.

Journal of Endocrinology (1991) 128, 475–482
GROWTH HORMONE RECEPTOR GENE: NOVEL EXPRESSION IN PITUITARY TISSUE
Authors: Fraser R.A. , Siminoski K. , Harvey S.
Published: December 2008

Specific hybridization of polyadenylated RNA, extracted from rat, rabbit and human pituitary glands with a 638 bp rabbit GH receptor (rGHR) cRNA was demonstrated by Northern analysis. In-situ hybridization of tissue sections with the probe demonstrated the localization of rGHR mRNA throughout the rat pituitary gland and its presence in the anterior lobe of the rabbit pituitary. Growth hormone binding sites on pituitary membranes were not, however, demonstrated by radioligand binding studies. Thus, although the GH receptor gene is expressed in pituitary tissue, functional GH receptors may not be inserted into pituitary plasma membranes.
ATRIAL NATRIURETIC FACTOR STIMULATES IN-VIVO AND IN-VITRO SECRETION OF CORTISOL IN TELEOSTS
Authors: Arnold-Reed D.E. , Balment R.J.
Published: December 2008

Atrial natriuretic factor (ANF) has been shown to increase circulating cortisol levels in cannulated, free-swimming seawater (SW)-adapted flounders. Increases were apparent within 30 min of i.v. injection of human ANF hANF; 10μg/kg bw) and the increase in plasma cortisol was maintained throughout the 5h experimental period. No such increase was observed in vehicle-injected controls. This apparent steroidogenic effect of ANF was supported by an ANF-induced increase in in-vitro secretion of cortisol by interrenal tissue from SW-adapted trout. By contrast hANF had no significant effect on tissue derived from freshwater adapted trout. An ANF-induced increase in plasma cortisol by a direct effect on interrenal steroidogenesis in SW teleosts would be an appropriate response for survival in hypertonic media.
Influence of oxytocin on sodium excretion in the anaesthetized Brattleboro rat
Authors: Brimble M. J. , Balment R. J. , Smith C. P. , Windle R. J. , Forsling M. L.
Published: December 2008

The contribution of oxytocin to the maintenance of renal Na+ excretion in the Brattleboro rat has been examined in animals infused with hypotonic saline. Brattleboro rats exhibited hypernatraemia and hyperosmolality associated with greatly increased plasma concentrations of oxytocin by comparison with Long–Evans control rats. Neurohypophysectomy to remove the secretion of the remaining posterior pituitary peptide, oxytocin, led to greatly diminished rates of Na+ excretion in the Brattleboro rat. Oxytocin replacement to achieve plasma levels equivalent to those in intact Brattleboro rats produced a substantial and sustained natriuresis in the neurohypophysectomized animal. Oxytocin secretion evoked in response to saline infusion would thus appear to be effective in promoting renal Na+ excretion in the absence of vasopressin in the Brattleboro rat.

Journal of Endocrinology (1991) 129, 49–54
Action of pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal polypeptide on the rat vascular system: effects on blood pressure and receptor binding
Authors: Nandha K. A. , Benito-Orfila M. A. , Smith D. M. , Ghatei M. A. , Bloom S. R.
Published: December 2008

The N-terminal fragment (PACAP 27) of the novel neuropeptide, pituitary adenylate cyclase-activating polypeptide 38 (PACAP 38), has 68% homology with vasoactive intestinal polypeptide (VIP). The administration of bolus doses of PACAP 38 and its 27 amino acid N-terminal fragment (PACAP 27) caused a rapid but transient dose-dependent hypotensive effect in the anaesthetized rat. The amplitude and duration of the response obtained by PACAP 38 was comparable with VIP whereas PACAP 27 was three times less potent than VIP. Furthermore, radioreceptor binding studies demonstrated that 125I-labelled PACAP 27 and 125I-labelled VIP bound to membranes prepared from blood vessels. Both PACAP 27 and VIP were capable of displacing the other from these binding sites. We propose that the hypotensive effect is via the same receptor type.

Journal of Endocrinology (1991) 129, 69–73
Hormonal regulation of epidermal growth factor and insulinlike growth factor-I in adult male hypophysectomized rats treated with ethane dimethane sulphonate
Authors: Spiteri-Grech J. , Bartlett J. M. S. , Nieschlag E.
Published: December 2008

There is increasing evidence implicating growth factors in the regulation of spermatogenesis and in-vitro studies have shown that epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) interact with the gonadotrophins in regulating testicular function. In the present study, the effect of FSH, testosterone and GH treatment on serum IGF-I and intratesticular EGF and IGF-I concentrations in adult male hypophysectomized rats treated with ethane dimethane sulphonate (EDS) to destroy Leydig cells has been investigated. Hypophysectomy alone or followed by EDS treatment was associated with a significant increase in intratesticular EGF concentrations compared with normal controls (P<0·05). Treatment of hypophysectomized animals with a combination of GH, FSH and testosterone resulted in a return of intratesticular EGF concentrations to normal control levels. In a second group of animals treated with a 5 cm silicone elastomer implant of testosterone and FSH, intratesticular EGF concentrations were also not significantly different from those of normal controls. Following hypophysectomy alone or hypophysectomy and EDS treatment, a significant increase in circulating IGF-I concentrations occurred, which was only reversed following the administration of GH. In addition, increases in testicular IGF-I concentrations were evident in all treated animals compared with controls, an effect which was only partially reversed in animals treated with a combination of FSH and testosterone (1·5 or 5 cm implant). Similar results were obtained with a combination of GH and FSH or GH and testosterone, although GH alone had no effect on testicular IGF-I concentrations. A combination of GH, FSH and testosterone restored testicular IGF-I to concentrations not significantly different from controls. It is suggested that GH, FSH and testosterone can play an important role in regulating circulating and testicular IGF-I and testicular EGF in the adult rat, but the regulation of growth factor production is a complex process and a number of other factors are probably involved in vivo.

Journal of Endocrinology (1991) 129, 109–117
Mechanisms responsible for suppression of FSH and LH during lactation in the rat
Authors: Taya K. , Sasamoto S.
Published: December 2008

Mechanisms responsible for suppression of FSH and LH secretion during lactation were investigated in rats, with special reference to the suckling stimulus and ovarian inhibin. Concentrations of immunoreactive inhibin in the peripheral plasma and bioactive inhibin in ovarian venous plasma were always low on days 3 and 5 of lactation in dams nursing eight pups, whereas values were always high on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. There was an FSH surge within 48 h after removal of litters on days 3 and 5 of lactation in dams nursing eight pups, whereas plasma concentrations of FSH were unchanged within 48 h by removal of litters on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. Plasma LH concentrations increased significantly compared with those of control animals within 24 h after removal of the litter on any day of lactation, regardless of the litter size.

Plasma FSH levels increased within 6 h after bilateral or unilateral ovariectomy in lactating rats only on the days when plasma concentrations of inhibin were high before ovariectomy, such as day 17 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas the mean concentrations of plasma LH showed no significant increase within 12 h after bilateral ovariectomy in these lactating rats. Treatment with progesterone or oestradiol-17β after unilateral ovariectomy did not inhibit the increase in plasma FSH levels, while the increase in plasma concentrations of FSH after surgery was completely inhibited by injecting inhibin (porcine follicular fluid). Treatment with steroid hormones inhibited the basal levels of LH in unilateral ovariectomized lactating rats. Plasma FSH concentrations increased sharply within 6 h after a single i.v. injection of anti-inhibin serum on days 10, 15 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas only a small but significant increase in concentrations of FSH was noted 6 h after the antiserum treatment on day 5 of lactation in dams nursing eight pups. Concentrations of plasma LH were unchanged by treatment with antiserum in lactating rats throughout lactation.

These findings indicate that the suckling stimulus, rather than ovarian factors, is mainly responsible for the suppression of FSH as well as LH secretion during the first half of lactation in rats nursing eight pups. On the other hand, during the second half of lactation in rats nursing eight pups and throughout lactation in rats nursing two pups, ovarian inhibin plays a primary role in the suppression of FSH secretion, whereas ovarian steroids act to suppress LH secretion.

Journal of Endocrinology (1991) 129, 119–130