bluuebunny/crossref_metadata_2025 huggingface dataset:
Dexamethasone and 8-bromo-cyclic AMP depress the incorporation of [3H]thymidine into mouse condylar cartilage by different pathways
Authors: Kraiem Z. , Maor G. , Silbermann M.
Published: December 2008

We examined whether cyclic AMP (cAMP) affects the incorporation of [3H]thymidine into cartilage cells and, if so, whether this action could be related to the inhibitory effect of glucocorticoid hormones on the growth of ossifying cartilage. Incorporation of [3H]thymidine into trichloroacetic acid-precipitable material by mouse cartilage was measured concomitantly with the concentration of cAMP. Dexamethasone (1 μmol/l) significantly (P < 0·05) depressed the incorporation of [3H]thymidine. The cAMP analogue 8-bromo-cAMP (0·01–1 mmol/l) also depressed the incorporation of the radionucleotide in a dose-dependent fashion. When various concentrations of 8-bromo-cAMP were added with dexamethasone (1 μmol/l), no apparent changes took place compared with the effect of dexamethasone alone. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0·2-1 mmol/l) elicited an inhibitory effect on [3H]thymidine incorporation and a stimulatory influence on cartilage cAMP concentrations. Dexamethasone, at doses (0·01–1 μmol/l) causing significant inhibition of [3H]thymidine incorporation, failed to increase cartilage levels of cAMP. It seems, therefore, that the depressive effect of dexamethasone on [3H]thymidine incorporation in condylar cartilage is not mediated through an increase of cAMP in the tissue.

J. Endocr. (1986) 109, 209–213
Regulation of the level of epidermal growth factor by oestrogen in the submandibular gland of female mice
Authors: Kurachi H. , Oka T.
Published: December 2008

The concentration of epidermal growth factor (EGF) in the submandibular gland of immature female mice (less than 6 weeks old) was low, ranging from 0·07 to 0·17 pmol (0·4 to 1·0 ng)/mg wet wt, but increasing to 7·61 pmol/mg wet wt by 8 weeks of age. It remained relatively constant up to 24 weeks of age, but thereafter the glandular EGF concentration increased again during the post-reproductive period to reach 62·9 pmol/mg wet wt. In contrast, the glandular EGF content in male mice increased greatly during the first 17 weeks of age to about 310 pmol/mg wet wt, and thereafter remained relatively constant up to 48 weeks of age. Ovariectomy of mature virgin mice markedly increased the glandular concentration of EGF to about 74·4 pmol/mg wet wt 4 weeks after the operation. This increase was suppressed by oestradiol-17β administered to ovariectomized mice at a dose of 1 μg/mouse per day but not by 1 mg progesterone. Histological studies indicated that granular convoluted tubular cells that produced EGF in the submandibular gland were much less abundant in 12-week-old female and in oestrogen-treated ovariectomized mature mice than in 40-week-old female and ovariectomized mature mice. We conclude that oestrogen suppresses the concentration of EGF in the submandibular gland of female mice.

J. Endocr. (1986) 109, 221–225
The actions of N-terminal fragments of corticotrophin on steroidogenesis in dispersed rat adrenal cells in vitro
Authors: Vinson G. P. , Whitehouse B. J. , Bateman A. , Dell A. , Laird S. M.
Published: December 2008

The finding that the rat adrenal zona glomerulosa cell shows specific sensitivity to stimulation by α-MSH and related peptides has been confirmed both in vivo and in vitro, raising the possibility that α-MSH may have a physiological role in the control of glomerulosa function and aldosterone secretion. To define more closely the structural features which confer the specificity of the glomerulosa response, other ACTH derived peptides have been tested for their specificity of actions on rat adrenal cells in vitro. The peptides tested were ACTH(5–24), ACTH(1–12), ACTH(1–14), ACTH(1–15), ACTH1–16) and ACTH(1–17). Their actions were compared with those of α-MSH and ACTH(1–24). All of the ACTH-derived peptides stimulated glomerulosa corticosterone production with sensitivities similar to that of α-MSH; minimum effective concentration was 10 nmol/l. Also, like α-MSH, the shorter ACTH peptides stimulated aldosterone production only relatively weakly in these cells from animals on normal sodium intake. Only ACTH(5–24), ACTH(1–16) and ACTH(1–17) stimulated fasciculata/reticularis cells at concentrations up to 1 μmol/l. The actions of all of the shorter peptides were thus unlike those of ACTH(1–24) which stimulates both cell types with approximately equal sensitivity, and which furthermore strongly stimulates aldosterone production.

The data suggest that the 18–24 region of the ACTH molecule contains the signal for a fasciculata/ reticularis response, and the region 1–13 that for glomerulosa specificity. They confirm the view that, in the rat, α-MSH itself may be the specific pituitary glomerulosa-stimulating agent which much experimental work has predicted. They also indicate that synthetic ACTH(1–17) analogues should be used with caution.

J. Endocr. (1986) 109, 275–278
Pulsatile growth hormone secretion in the ovine fetus and neonatal lamb
Authors: Bassett N. S. , Gluckman P. D.
Published: December 2008

The ontogenesis of the pulsatility of GH in the ovine fetus was determined by obtaining blood samples at 20-min intervals for 3-h periods from fetuses (n = 33) at various stages of development (76–147 days gestation), and in neonatal life (n = 19). A significant increase (P <0·01) in the GH mean, nadir and maximum, and pulse height was observed between the ages of 100 and 130–139 days of gestation. An analysis of the difference in the mean, maximum and nadir concentrations between 100 and 139 days of gestation revealed that males had higher GH levels than females (P <0·05).

There was a significant fall in plasma GH concentrations from 140 days of gestation to term, but before the onset of active labour. There was a more rapid fall in the circulating levels of fetal GH directly following birth. Immediately before birth fetal GH levels were still relatively high, but within 60 min of birth they had fallen by more than 80%.

It is suggested that these changes in the pulsatile pattern of GH release are a consequence of both maturational changes in the hypothalamic-pituitary unit and the effects of pregnancy-related factors on GH release. The sexually dimorphic nature of GH release in the adult is also observed in the sheep fetus during late gestation.

J. Endocr. (1986) 109, 307–312
Kinetics of transfer of 125I-labelled epidermal growth factor from blood into mammary secretions of goats
Authors: Brown K. D. , Blakeley D. M. , Fleet I. R. , Hamon M. , Heap R. B.
Published: December 2008

125I-Labelled mouse epidermal growth factor (125I-EGF) was transferred intact and undegraded from circulating blood into milk in conscious lactating goats. Greater than 90% of the total radioactivity present in milk from the infused gland was in the aqueous phase and more than 72% was acidprecipitable. This radiolabelled material co-eluted with authentic EGF through gel filtration and was immunoprecipitable by a specific rabbit anti-mouse EGF immunoglobulin. Mammary uptake of125I-EGF infused into mammary arterial blood (close-arterial infusion) for 1 h varied from 20 to 83% at different stages of the reproductive cycle. Only 0·5–2·9% of the infused 125I-EGF was transferred into milk during the first 3 h after the start of the infusion, which represents 0·7–6·3% of mammary uptake of EGF.

The kinetics of transfer of 125I-EGF were followed in two lactating goats. Radioactivity reached peak levels in milk about 120 min after the start of a 1 h close-arterial infusion into the mammary gland, with an initial lag of about 30 min when little transfer occurred. Transfer was slower in two non-lactating goats with maximal levels of activity in milk being reached after about 180 min. The results are consistent with a transcellular transfer, whereby the factor is bound to receptors on the baso-lateral membrane, internalized by epithelial cells and subsequently secreted across the apical membrane into the alveolar lumen. The low level of degraded labelled EGF in milk (and mammary vein blood) suggests a modification of the normal pathway of EGF degradation such that the delivery of internalized factor to lysosomes is avoided.

J. Endocr. (1986) 109, 325–332
Dopamine effects on adrenocorticotrophin-stimulated aldosterone, cortisol, corticosterone and 11-deoxycorticosteroid concentrations in sodium-replete and sodium-deplete man
Authors: Connell J. M. C. , Kenyon C. J. , Ball S. G. , Davies D. L. , Fraser R.
Published: December 2008

The effect of dopamine (1 μg/kg per min) on corticosteroid response to ACTH (0·1, 1 and 10 ng/kg per min) was compared with that of a placebo in sodium-replete (150 mmol/day) and -deplete (10 mmol/day) normal man. Dopamine had no effect on aldosterone, cortisol or corticosterone responses in either dietary phase, but increased deoxycorticosterone (897·0 ± 126·4 (s.e.m.) vs 590·0 ±84·3 pmol/l, normal Na+; 1264·2 ±84·3 vs 764·5 ±84·3 pmol/l, low Na+) and deoxycortisol (6·033 ± 0·583 vs 5·048±0·680 nmol/l, normal Na+; 5·112 ± 0·600 vs 4·130± 0·367 nmol/l, low Na+) levels during ACTH administration (all P <0·01). Deoxycorticosterone and corticosterone responses to ACTH were greater during sodium depletion than repletion (both P <0·01).

Dopamine therefore increased 11-deoxycorticosteroid concentrations during ACTH-stimulated steroidogenesis. This may reflect action of dopamine to increase extra-adrenal formation of 11-deoxycorticosteroids.

J. Endocr. (1986) 109, 339–344
Hypothyroidism of hypothalamic origin in pyridoxine-deficient rats
Authors: Dakshinamurti K. , Paulose C. S. , Vriend J.
Published: December 2008

Pyridoxine-deficient young rats (3 weeks old) had significantly reduced levels of pituitary TSH, serum thyroxine (T4) and tri-iodothyronine (T3) compared with pyridoxine-supplemented rats. The status of the pituitary-thyroid axis of normal, pyridoxine-supplemented and pyridoxine-deficient rats was evaluated by studying the binding parameters of [3H](3-methyl-histidine2)TRH in the pituitary of these rats. The effects of TRH and T4 injections on pituitary TSH and serum TSH, T4 and T3 of these two groups were also compared. The maximal binding of TRH receptors in the pituitary of pyridoxine-deficient rats was significantly higher than that of pyridoxine-supplemented control and normal rats, but there was no change in the binding affinity. Treatment with TRH stimulated TSH synthesis and release. It also increased serum T4 and T3 in both pyridoxine-supplemented and pyridoxine-deficient rats. Treatment with T4 decreased serum and pituitary TSH in both pyridoxine-supplemented and pyridoxine-deficient rats, compared with saline-treated rats. The increased pituitary TRH receptor content, response to TRH administration and the fact that regulation at the level of the pituitary is not affected in the pyridoxine-deficient rat indicates a hypothalamic origin for the hypothyroidism of the pyridoxine-deficient rat.

J. Endocr. (1986) 109, 345–349
Effects of porcine relaxin on oxytocin release from the neurohypophysis in the anaesthetized lactating rat
Authors: O'Byrne K. T. , Eltringham L. , Clarke G. , Summerlee A. J. S.
Published: December 2008

The effect of relaxin on electrically evoked release of oxytocin from the posterior pituitary was examined by monitoring changes in intramammary pressure in the anaesthetized lactating rat.

The amount of oxytocin released by electrical stimulation of the neurohypophysis in vivo was dramatically reduced following i.v. injection of highly purified porcine relaxin (2·5–10 μg/rat). Relaxin inhibited oxytocin release in a dose-dependent manner and the onset of inhibition occurred within 6–10 min and lasted for 10–60 min. No effect on the sensitivity of the mammary gland to exogenous oxytocin was observed after relaxin treatment. During the period of inhibition, i.v. injection of the opioid antagonist naloxone chloride (1 mg/kg) completely and immediately restored electrically evoked oxytocin release. The neurohypophysis is known to contain endogenous opioid peptides, therefore the effect of relaxin on electrically stimulated release of oxytocin from the rat isolated neural lobe in vitro was examined. Relaxin (500–2000 ng/ml) failed to inhibit oxytocin release in vitro.

The results suggest that relaxin can inhibit the release of oxytocin from terminals in the neurohypophysis, but by an indirect mechanism. This action appears to be mediated through endogenous opioid peptides whose source is not clear. They are unlikely to be of neurohypophysial origin and may probably come from the adrenal medulla, since acute adrenalectomy negated the inhibitory effect of relaxin on oxytocin release.

J. Endocr. (1986) 109, 393–397
Seminiferous tubule androgen receptors in experimental cryptorchidism
Authors: Winters S. J.
Published: December 2008

As an initial approach to the study of seminiferous tubule androgen receptors in disordered spermatogenesis, cytosol androgen receptors were studied in rats with experimental cryptorchidism. Two weeks after the testis had been repositioned in the abdomen of 6-week-old rats, the animals were hypophysectomized to deplete the testis of androgen, and 1 week later they were killed. Androgen receptor binding was studied in seminiferous tubule cytosol using [3H]methyltrienolone as the radiolabelled probe. The androgen-binding capacity of cryptorchid testis, when expressed as fmol bound/testis, was reduced to 50% of control, in parallel with the decline in testis weight. No change in binding affinity was found. Sucrose density gradient centrifugation using a vertical tube rotor revealed a 9S molybdate-stabilized receptor under low-salt conditions in both cryptorchid and scrotal seminiferous tubule cytosol. Receptor-complex stability studies, analysis by gel filtration and DEAEcellulose chromatography produced similar results in cryptorchid and scrotal tubules. The mechanism for the reduction in testicular receptor content of an abdominal testis remains to be clarified. The demonstration that testicular androgen receptors can be reduced by cryptorchidism suggests that further studies may indicate the role of receptor binding in testicular function.

J. Endocr. (1986) 109, 427–433
EVIDENCE FOR GRANULOSA-THECA INTERACTION IN THE SECRETION OF OXYTOCIN BY BOVINE OVARIAN TISSUE
Authors: Jungclas B. , Luck M.R.
Published: December 2008

We have examined the ability of granulosa cells, from carefully selected preovulatory bovine follicles, to secrete oxytocin in vitro. Although cells from 83% of follicles underwent functional luteinisation (greatly increased progesterone secretion) in serum-supplemented culture, only 69% had cells capable of oxytocin secretion. Secretion followed a similar time course in all cultures, with the peak appearing on day 3. Oxytocin, but not progesterone, output could be consistently increased by addition of pieces of theca interna tissue, or theca conditioned medium, to the cultures. The effect could be achieved by exposure to theca tissue at any time prior to peak output without altering the time course of secretion. Oxytocin could not be detected in follicular fluid from any of the selected follicles, nor in medium from theca cultured alone. We conclude that the potential for oxytocin secretion is a feature of follicular maturation which is lost during atresia and that the stimulus to secretion is associated with luteinisation but not with progesterone output. Finally, the intermixing of follicular cells during corpus luteum formation may provide a mechanism for the enhancement of oxytocin secretion within a predetermined time frame.
Effects of hypophysectomy and growth hormone infusion on rat hepatic carbonic anhydrases
Authors: Jeffery S. , Wilson C. A. , Mode A. , Gustafsson J.-Å. , Carter N. D.
Published: December 2008

Rat liver exhibits a reversed sexual dimorphism of its two endogenous soluble carbonic anhydrase (CA) isozymes, CA II and CA III. Normal males have hepatic CA III concentrations ten–twenty times those in the female, while female liver contains two–three times more CA II than the male. Hypophysectomy abolishes this sexual differentiation, having no effect on male liver but producing isozyme concentrations in the female liver similar to those in the male. Infusion of a continuous level of GH into male rats induces a female-like isozyme pattern for both CA II and CA III.

J. Endocr. (1986) 110, 123–126
Field evaluation of a pregnancy immunoassay for the detection of oestrone sulphate in goats
Authors: McArthur C. P. , Geary A.
Published: December 2008

The concentration of oestrone sulphate in whey obtained from 66 pregnant dairy goats was measured by direct radioimmunoassay. The mean time at which pregnancy was first detected was day 41 of gestation. Levels remained low (37 pmol/l–0·96 nmol/l, mean = 167 pmol/l) until week 5 of gestation when they rose rapidly. The test had an accuracy of 95·6%, was able to distinguish true from pseudopregnancy, and suggested that pregnancy in females carrying multiple fetuses could be detected earlier, possibly as a result of the fetal-placental origin of oestrone sulphate.

J. Endocr. (1986) 110, 133–136
Radioimmunoassay of pineal 5-methoxytryptophol in different species: comparison with pineal melatonin content
Authors: Skene D. J. , Smith I. , Arendt J.
Published: December 2008

A sensitive, specific, reproducible and practical radioimmunoassay for the determination of 5-methoxytryptophol (ML) in pineal glands of different species has been developed. High-affinity specific antisera were produced by immunization of sheep with ML–bovine serum albumin. Iodinated ML, used as the radiolabel, was synthesized by direct iodination of ML using 1,3,4,6,-tetrachloro-3,6-diphenylglycouril as the oxidant. Sensitivity of the assay was 0·005 pmol/tube. The validity of the assay was checked using classical techniques. Cross-reactivity with other indoles was negligible. Parallel inhibition curves were obtained for rat, hamster, sheep and tortoise pineal homogenates. Using thin-layer chromatography, tortoise pineal immunoreactivity also co-chromatographed with standard ML. Samples (n = 5) with ML concentrations of 0·013, 0·052 and 0·209 pmol/tube had intra-assay coefficients of variation of 9·8, 5·7 and 7·6% respectively. Their respective interassay coefficients of variation were 17·7 16·5 and 11·4% (n = 8). The pineal concentration of ML was found to be species dependent. Afternoon ML levels were 0·052± 0·002 (s.e.m.) pmol/gland in the rat (n = 16), 0·539 ±0·089 pmol/gland in the hamster (n = 16), 1·73±0·225 nmol/g in the sheep (n = 10) and 7·15± 0·465 pmol/gland in the tortoise (n = 4). The ratio of ML:melatonin content in the pineal gland also showed a large interspecies variation with values of 0·02 in the rat, 0·22 in the sheep, 2·7 in the hamster and 17 in the tortoise.

J. Endocr. (1986) 110, 177–184
Gestational changes in the level of glucocorticoid-binding sites in fetal bovine cartilaginous tissues
Authors: Kan K. W. , Cruess R. L.
Published: December 2008

In order to assess glucocorticoid actions on fetal cartilage development, [3H]dexamethasone binding site levels in fetal bovine cartilaginous tissues from long bones were measured, using a whole cell assay at 37 °C. Displaceable [3H]dexamethasone binding in epiphysial growth cartilage was maximal (16·2 fmol/106 cells) in fetuses of 10–15 cm crown–rump length (CR), and declined to 22% of the maximum in fetuses of 20–30 cm CR. Subsequently, [3H]dexamethasone binding rose to a plateau (13·0 fmol/106 cells) in fetuses of 30–80 cm CR and declined in those of 80–100 cm CR. When measured in growth plate cartilage, [3H]dexamethasone binding was significantly higher in fetuses of 40–80 cm CR (39 fmol/106 cells) than in those of 80–100 cm CR. There was no significant change of [3H]dexamethasone binding affinities in epiphysial chondrocytes of 5–100 cm CR fetuses or in growth plate chondrocytes of 40–100 cm CR fetuses.

These results demonstrate that fetal cartilaginous tissues during development possess varying cellular levels of glucocorticoid binding and may thus have temporal changes in sensitivity to glucocorticoid hormones.

J. Endocr. (1986) 110, 257–262
Initiation of ovarian follicular maturation without a surge of FSH in cyclic rats treated with antiserum to LH-releasing hormone
Authors: Matsuzono N. , Taya K. , Watanabe G. , Sasamoto S.
Published: December 2008

The relationship between a surge of FSH and the initiation of follicular maturation was examined using rats with a 4-day oestrous cycle. When antiserum against LH-releasing hormone (LHRH-AS) was given at 13.00 h on the day of pro-oestrus (day 0), surges of FSH and LH were blocked. Plasma FSH and LH were maintained at low basal levels without a surge release until the next spontaneous surge occurred on the afternoon of day 4, the predicted day of pro-oestrus. Follicular responsiveness to an injection of human chorionic gonadotrophin (hCG) indicated that preovulatory follicles, present at the time of treatment with LHRH-AS, were capable of ovulating on day 1 but had regressed by day 2. Subsequently, as shown by the ovulatory response to hCG, a new set of follicles had begun to mature by the morning of day 3 without a preceding surge of FSH. Changes in oestradiol-17β levels in the plasma throughout the oestrous cycle were the same in rats injected with LHRH-AS or non-immune control serum. The mature follicles in the rats treated with LHRH-AS thus retained the capacity to ovulate after losing their ability to secrete oestrogen.

These results suggest that an FSH surge is not essential for initiation of follicular maturation and that basal levels of FSH may be enough to initiate follicular maturation in the absence of newly formed corpora lutea.

J. Endocr. (1986) 110, 279–285
Effect of hydrogen ion concentration on aldosterone secretion by isolated perfused canine adrenal glands
Authors: Radke K. J. , Taylor R. E. , Schneider E. G.
Published: December 2008

The direct effects of changes in extracellular hydrogen ion (H+) concentration on aldosterone secretion under basal, angiotensin II- and potassium-stimulated conditions were studied in isolated, perfused canine adrenal glands. Changes in extracellular H+ concentration were induced by altering either the partial pressure of CO2 (pCO2) or the HCO3− concentration of the perfusate. Acid-base disturbances had a more pronounced effect on aldosterone secretion under stimulated than under basal conditions. Increasing H+ concentration enhanced angiotensin II- and potassium-stimulated aldosterone secretion, whereas decreasing H+ concentration markedly inhibited the secretory response to these stimuli. Because changes in H+ concentration, whether produced by varying extracellular pCO2 or extracellular HCO3− concentration, had similar effects on angiotensin II-stimulated aldosterone secretion, the data suggest that H+ concentration per se is the important determinant of the aldosterone secretory rate. Interestingly, during the immediate recovery period from pCO2-induced alkalosis under both angiotensin II- and potassium-stimulated conditions, aldosterone secretion always returned to a value significantly higher than that obtained just before alkalosis. The results of this study demonstrate that changes in extracellular H+ concentration influence the rate of aldosterone secretion, possibly via changes in intracellular pH, by a direct action on the canine adrenal gland. Therefore, when evaluating the control of aldosterone secretion, the acid-base status of the whole animal or of in-vitro adrenal tissue must be considered.

J. Endocr. (1986) 110, 293–301
Establishment of a continuous somatostatin-producing line of medullary thyroid carcinoma cells from BALB/c mice
Authors: Tischler A. S. , Lee Y. C. , Costopoulos D. , Nunnemacher G. , DeLellis R. A. , Van Zwieten M. J. , Wolfe H. J. , Bloom S. R.
Published: December 2008

A continuous line of somatostatin-producing medullary thyroid carcinoma cells was established from a transplantable tumour in BALB/c mice. Virtually all of the somatostatin immunoreactivity co-chromatographed with somatostatin 14. The tumour cells replicated in spinner cultures with a doubling time of approximately 4 days, and the concentration of somatostatin released into the culture medium increased in proportion to the number of cells. Two-to threefold increases in amounts of stored and released somatostatin were observed after treatment of the cells with bromodeoxyuridine. This cell line might be valuable for studies of somatostatin regulation in normal and neoplastic C-cells, and for other studies of C-cell biology which require a mouse model.

J. Endocr. (1986) 110, 309–313
Unique calcium dependencies of the activating mechanism of the early and late aldosterone biosynthetic pathways in the rat
Authors: Schiebinger R. J. , Braley L. M. , Menachery A. , Williams G. H.
Published: December 2008

This study compared the extracellular calcium dependency and the enzymatic locus of that dependency for N6,O2′-dibutyryl cyclic AMP (dbcAMP)-, angiotensin II- and potassium-stimulated aldosterone secretion in dispersed rat glomerulosa cells. The need for extracellular calcium, calcium influx, and specifically for calcium influx through the calcium channel was examined. dbcAMP, angiotensin II and potassium, in the presence of calcium (3·5 mmol/l), significantly (P < 0·01) increased aldosterone output by at least 1·5-fold. Yet in the absence of extracellular calcium or in the presence of lanthanum (an inhibitor of calcium influx by most mechanisms) all three stimuli failed to increase aldosterone secretion. Nifedipine, a dihydropyridine calcium channel antagonist, significantly (P < 0·01) reduced angiotensin II- and potassium-stimulated aldosterone secretion, but had no effect on dbcAMP-stimulated aldosterone secretion (100 ± 14 vs 105 ± 19 pmol/106 cells). Likewise nitrendipine failed to inhibit ACTH-stimulated aldosterone secretion.

Angiotension II and potassium activation of both the early aldosterone biosynthetic pathway (as reflected by pregnenolone production in the presence of cyanoketone) and also its late pathway (as reflected by the conversion of exogenous corticosterone to aldosterone in the presence of cyanoketone) were significantly (P < 0·01) inhibited by lanthanum, nifedipine and by reducing the extracellular calcium concentration. However, with dbcAMP stimulation, none of these manipulations modified pregnenolone production. Late pathway activation by dbcAMP was inhibited by lanthanum and a reduction in extracellular calcium, but not by nifedipine.

These observations suggest that: (1) the extracellular calcium dependency of dbcAMP-, angiotensin II- and potassium-stimulated aldosterone secretion reflects a need for calcium influx; (2) with dbcAMP stimulation, activation of the late pathway is dependent on calcium influx by a calcium channel-independent mechanism, whereas activation of the early pathway is not dependent on extracellular calcium or calcium influx and (3) activation of both the early and late pathway by angiotensin II and potassium is dependent on calcium influx by a calcium channel-dependent mechanism. Therefore, we conclude that the mechanism of activation of the early aldosterone biosynthetic pathway by dbcAMP is different from angiotensin II or potassium and early pathway activation is distinct from that of late pathway activation with dbcAMP stimulation.

J. Endocr. (1986) 110, 315–325
Vasopressin, but not oxytocin, is released in response to water deprivation in conscious goats
Authors: Thornton S. N. , Leng G. , Bicknell R. J. , Chapman C. , Purdew T.
Published: December 2008

Plasma samples obtained at 4-h intervals from goats for at least 24 h before and then during 24 h of deprivation of water were analysed by radioimmunoassay for vasopressin and oxytocin concentrations. The samples were also analysed for osmolality and sodium concentration. The differential effect of night/day versus day/night deprivation was also studied. During the two periods before the two deprivations osmolality varied in a regular manner, with low values occurring at 08.00 h. Sodium concentration followed osmolality, whereas vasopressin did not vary during the period before deprivation. During deprivation vasopressin increased along with osmolality and sodium concentration, with the beginning of the increase occurring after the morning feed. Oxytocin levels did not increase during the period of deprivation.

These results do not support the hypothesis of general release of neurohypophysial hormones in response to osmotic stimuli but instead indicate there are species variations with respect to hormonal response to water deprivation.

J. Endocr. (1986) 110, 335–340
Measurement of exogenous and endogenous inhibin in sheep serum using a new and extremely sensitive bioassay for inhibin based on inhibition of ovine pituitary FSH secretion in vitro
Authors: Tsonis C. G. , McNeilly A. S. , Baird D. T.
Published: December 2008

An extremely sensitive and reliable bioassay for inhibin based on inhibition of ovine pituitary FSH secretion in vitro was developed and used to measure exogenous and endogenous inhibin activity in the ewe. The sheep inhibin bioassay is 30- to 40-fold more sensitive than conventional rat inhibin bioassays. The minimum sensitivity of each bioassay in the measurement of inhibin activity in 1 ml of sheep serum is 220 mu. and 4080 mu. in the sheep and rat bioassays respectively. This sensitive inhibin bioassay has permitted, for the first time, the measurement of endogenous inhibin in the peripheral and ovarian vein blood of the sheep, as well as exogenously administered inhibin.

The half-life of exogenously administered ovine inhibin (in follicular fluid) in the sheep was calculated as two components (18–24 and 50–60 min) from the inhibin profiles of six ewes. Inhibin contained in the ovine follicular fluid, given as a bolus i.v. injection, increased to maximum levels after 5 min and then remained increased for 10–32 min depending upon the dose administered, before exponentially decaying. The time for inhibin to exert its effect ranged from 3 to 6 h after injection and appeared to be dose-related. The bolus injection of inhibin, apart from causing suppression of FSH, evoked a large rebound increase of FSH up to 400% of preinjection levels.

The development of the sheep bioassay will allow the measurement of biologically active inhibin in the peripheral circulation and ovarian vein blood of sheep with the possibility of extending this to man.

J. Endocr. (1986) 110, 341–352
Effects of long- and short-term gonadectomy on the hypothalamo-hypophysial (LH-releasing hormone–LH) system in oestrogen-treated male and female rats
Authors: Weiland N. G. , Barraclough C. A. , Catt K. J.
Published: December 2008

Considerable differences have previously been found in the hypothalamo-hypophysial responsiveness to oestrogen, depending upon the time between gonad removal and exposure to oestrogen. In the present study a detailed analysis was made of some of the differences which may exist in pituitary LH-releasing hormone (LHRH) receptors and the amount of LH released in response to electrochemical depolarization of the medial preoptic area after 2 or 7 days of oestradiol treatment of long- and short-term gonadectomized male and female rats. The pituitary glands of long-term gonadectomized males and females secreted more LH in response to two pulse injections of LHRH than did short-term gonadectomized rats. The amount of LH released on day 2, however, was equivalent to that secreted after 7 days of oestradiol treatment. Moreover, long-term gonadectomized males and females had equivalent LHRH receptor concentrations, which were greater than those of short-term gonadectomized animals. Peak serum LH concentrations observed after preoptic stimulation were equivalent in short- and long-term castrated rats after 2 days of oestrogen exposure. Serum LH concentrations following preoptic stimulation in short-term gonadectomized males and females were significantly greater on day 7 than on day 2 of oestradiol treatment, whereas in long-term gonadectomized animals the stimulated release of LH was equivalent both in magnitude and time of peak release on both days.

These studies demonstrate that the differential effects of oestradiol on LH release on day 2 (no negative feedback) compared with day 7 (both negative and positive feedback exist) are not due to differences in the ability of the pituitary gland to release LH in response to LHRH, nor in the releasable pools of hypothalamic LHRH in long-term gonadectomized rats. Rather, they seem to be due to a refractoriness in some unidentified central nervous process which regulates tonic LH release in gonadectomized rats.

J. Endocr. (1986) 110, 367–373
In-vivo studies of a human-thyrotrophin preparation
Authors: Law A. , Jack G. W. , Tellez M. , Edmonds C. J.
Published: December 2008

The effects on thyroid function of a new preparation of human thyrotrophin (hTSH) were studied in four subjects whose endogenous production of TSH had been suppressed by administration of thyroxine (T4). The hTSH, prepared from human cadaveric pituitary glands and highly purified using a monoclonal antibody technique, was given as an intravenous bolus of 2 i.u. hTSH. Serum TSH levels rose rapidly to a maximum of about 150 mu./l and then declined exponentially with a half-life of 100 min. After injection, the hTSH distributed rapidly in a volume averaging about 13 litres which corresponded approximately to the expected extracellular fluid volume of the subjects. Serum free tri-iodothyronine and free T4 rose significantly, reaching a maximum between 4 and 8 h after injection of hTSH; serum thyroglobulin was not altered significantly. The rise of thyroid pertechnetate uptake, a measure of the thyroid iodide uptake, occurred later, being only slightly increased at 8 h after administration of hTSH and reaching a maximum at 24 h.

J. Endocr. (1986) 110, 375–378
Dopamine does not attenuate phosphoinositide hydrolysis in rat anterior pituitary cells
Authors: Canonico P. L. , Jarvis W. D. , Judd A. M. , MacLeod R. M.
Published: December 2008

The hydrolysis of membrane phosphatidylinositol to yield [3H]labelled inositol phosphates by anterior pituitary cells was stimulated significantly by angiotensin II, TRH and neurotensin over a broad range of concentrations. These secretagogues also stimulated release of prolactin. Although the coincident incubation of dopamine with these agents resulted in a marked diminution of prolactin release, no concomitant reduction in inositol phosphate production was observed. In addition, bromocriptine, a potent agonist of dopamine, also proved ineffective in blunting stimulated phosphatidylinositol catabolism. Although it slightly inhibited basal rates of inositol tris-, bis- and monophosphate production, these results show that the secretagogue-mediated enhancement of phosphatidylinositol catabolism may be correlated with an increased release of prolactin and that the inhibition of hormone release produced by dopamine is not achieved by reducing basal or secretagogue-mediated inositol phosphate production.

J. Endocr. (1986) 110, 389–393
Effects of α-melanocyte-stimulating hormone on the cyclic AMP and phospholipid metabolism of rat adrenocortical cells
Authors: Hyatt P. J. , Bell J. B. G. , Bhatt K. , Chu F. W. , Tait J. F. , Tait S. A. S. , Whitley G. St J.
Published: December 2008

Results on the effects of peptides on the phospholipid metabolism and steroid and cyclic AMP (cAMP) outputs of rat adrenal capsular cells (96% zona glomerulosa, 4% zona fasciculata) were obtained in a series of three batch experiments. Their significance was examined by analysis of variance. Incorporation of [32P] into phosphatidylcholine, phosphatidic acid and phosphatidylinositol was measured. Production of [3H]inositol-1 monophosphate, inositol-1,4 bis-phosphate and inositol-1,4,5 tris-phosphate was estimated after prelabelling with [3H]inositol followed by 1 min incubation with a steroidogenic stimulus. Angiotensin II (0·25 nmol/l to 0·25 μmol/l) highly significantly (P < 0·01) stimulated aldosterone and corticosterone outputs, [32P] incorporation into phosphatidic acid and phosphatidylinositol (but not into phosphatidylcholine) and the production of the three [3H]inositol phosphates. Aldosterone and corticosterone outputs were stimulated by α-MSH (above 0·1 nmol/l). However, incorporation of [32P] was not significantly increased until 10 μmol α-MSH/l but, unlike with angiotensin II, incorporation into phosphatidylcholine was also then stimulated. Also, the production of the inositol phosphates was not increased significantly (P > 0·05) by any dose of α-MSH (10 nmol/l, 1 μmol/l and 0·1 mmol/l) used. Therefore, it can be concluded that α-MSH does not stimulate phospholipase C in rat zona glomerulosa cells. In further experiments, it was also found that there were significant increases in cAMP as well as in steroid outputs above 1 nmol α-MSH/l (highly significant above 10 nmol α-MSH/l). There were plateaux of the outputs of both steroids and cAMP from 0·1 to 1 μmol α-MSH/l. However, there were further increases in steroid and cAMP outputs of the capsular cells at higher doses. Concomitant results on the stimulation of corticosterone output by zona fasciculata–reticularis cells indicate that this additional increase was mostly due to the stimulation of the contaminating zona fasciculata cells. It was also confirmed that α-MSH preferentially stimulates steroidogenesis by the zona glomerulosa. However, under our conditions, α-MSH highly significantly increased the output of cAMP by both zona fasciculata and glomerulosa cells.

J. Endocr. (1986) 110, 405–416
In-vitro conversion of thyroxine to tri-iodothyronine by chicken hepatic 5′-deiodinase: kinetic studies
Authors: Lam S. K. , Harvey S.
Published: December 2008

In-vitro studies with chicken liver homogenates demonstrate that the conversion of thyroxine (T4) to tri-iodothyronine (T3) is dependent upon tissue concentration, time of incubation, pH, temperature, the presence of dithiothreitol (DTT) and the concentration of substrate (T4), and is heat-labile. The generation of T3 is inhibited by iopanoic acid and 6-n-propyl-2-thiouracil. The kinetics of conversion of T4 to T3, determined by Lineweaver–Burke analysis, indicated an apparent Michaelis–Menten constant (Km) of 1·16 μmol/l with a maximum velocity (Vmax) of 44·57 pmol T3 generated/mg protein per min from T4. Dithiothreitol appears to behave as a co-substrate for this system with an apparent Km of 98·5 μmol/l and a Vmax of 1·41 pmol T3 generated/mg protein per min at a T4 concentration of 5 μmol/l. These data suggest that the conversion of T4 to T3 in fowl proceeds by means of an enzymatic system, probably 5′-monodeiodinase, and is responsible for maintaining T3 levels in vivo.

J. Endocr. (1986) 110, 441–446.
Analysis of prostatic bud induction by brief androgen treatment in the fetal rat urogenital sinus
Authors: Takeda H. , Lasnitzki I. , Mizuno T.
Published: December 2008

The androgen dependency of prostatic bud formation in fetal rat urogenital sinuses was studied using brief treatments with androgen, and the incorporation of androgens by the sinus mesenchyme was followed by steroid autoradiography.

Urogenital sinuses from 16·5-day fetuses of both sexes were grown in organ culture and treated with androgens for periods ranging from 4 to 72 h and then transferred to control medium. A minimum treatment of 24 h was required to induce prostatic buds in male sinuses and of 36 h in all female sinuses. This difference in response disappeared after more prolonged treatment. In both sexes the number of prostatic buds increased with the time of exposure to androgens. Prostatic bud formation continued for 24–36 h after transfer to control medium.

Steroid autoradiographic analysis showed that the labelled androgen was concentrated in the mesenchymal nuclei. The rate of incorporation rose steeply during the first 12 h and then more slowly. After transfer to control medium the amount of labelled androgen decreased rapidly to half within 12 h and then decreased more slowly. In the competition experiments a 200-fold excess of unlabelled testosterone or dihydrotestosterone in the labelling medium greatly reduced the nuclear labelling with [3H]testosterone.

J. Endocr. (1986) 110, 467–470
Are catechol oestrogens obligatory mediators of oestrogen action in the central nervous system? I. Characterization of pharmacological probes with different receptor binding affinities and catechol oestrogen formation rates
Authors: Pfeiffer D. G. , MacLusky N. J. , Barnea E. , Naftolin F. , Krey L. C. , Loriaux D. L. , Merriam G. R.
Published: December 2008

In an attempt to define pharmacological probes with which to test the role of catechol oestrogen formation in the central nervous system, five oestrogens (oestradiol-17β, oestradiol-17α, 4-fluoro-oestradiol, 2-fluoro-oestradiol and moxestrol (11β-methoxy-17α-ethynyloestradiol) were studied for binding to oestrogen receptors and conversion to catechol metabolites. Binding to cytosol oestrogen receptors was measured in the hypothalamus–preoptic area–amygdala (HPA), pituitary gland and uterus of ovariectomized rats. Conversion to catechol oestrogens was tested in microsomes from the HPA, pituitary gland and liver, using a catechol-O-methyltransferase-coupled radioenzymatic assay. Oestradiol-17α was the only weak oestrogen receptor ligand. Binding affinities of the other compounds tested were much higher and comparable to those of oestradiol-17β. In contrast, oestradiol-17α was rapidly converted to catechol metabolites, while moxestrol was a relatively poor substrate for catechol oestrogen formation. 4-Fluoro-oestradiol could be 2-hydroxylated but not 4-hydroxylated. 2-Fluoro-oestradiol exhibited impaired 2-hydroxylation but normal 4-hydroxylation.

J. Endocr. (1986) 110, 489–497
Are catechol oestrogens obligatory mediators of oestrogen action in the central nervous system? II. Potencies of natural and synthetic oestrogens for induction of gonadotrophin release and female sexual behaviour in the rat
Authors: MacLusky N. J. , Krey L. C. , Parsons B. , Merriam G. R. , Loriaux D. L. , Pfeiffer D. G. , Naftolin F.
Published: December 2008

The role of catechol oestrogen formation in the mechanism by which circulating oestrogens facilitate gonadotrophin release and female sexual behaviour was explored in adult female rats. The effects of oestradiol-17β were compared with those of a group of oestrogens with either a reduced affinity for oestrogen receptors (oestradiol-17α) or a reduced ability to act as substrates for catechol oestrogen formation (2-fluoro-oestradiol, 4-fluoro-oestradiol and moxestrol (11β-methoxy-17α-ethynyloestradiol)). Rats were ovariectomized on the evening of dioestrus day 1 of the 4-day oestrous cycle and implanted s.c. 12 h later with infusion pumps containing either one of the test oestrogens or vehicle alone. Infusion rates for oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol were adjusted to give concentrations of nuclear oestrogen receptors in the brain and pituitary gland within the range of those found in intact female rats during pro-oestrus. Oestradiol-17α was infused at the same and at a tenfold higher rate than that of oestradiol-17β; neither of these treatments with oestradiol-17α significantly increased brain or pituitary gland nuclear oestrogen receptor levels. On the day after the pump was implanted, samples of tail vein blood were withdrawn at 12.00, 14.00, 16.00 and 18.00 h for LH assay. All animals were then injected s.c. with 1 mg progesterone in propylene glycol, and tested for feminine sexual behaviour 5 h later. Oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol all elicited pronounced LH surges and facilitated progesterone-triggered proceptive and lordosis behaviours. In contrast, oestradiol-17α was without effect on LH secretion and sexual behaviours. These results are consistent with the hypothesis that catechol oestrogen biosynthesis is not an obligatory step in the mechanism by which circulating oestrogens induce LH release and feminine sexual behaviour in the rat.

J. Endocr. (1986) 110, 499–505
Effect of age on the 3,5,3′-tri-iodothyronine-induced increase in sugar uptake in rat thymocytes
Authors: Segal J. , Troen B. R.
Published: December 2008

The effect of age on the responsiveness of rat thymocytes to 3,5,3′-tri-iodothyronine (T3) was studied. It has been demonstrated previously that the plasma membrane-mediated effect of T3 to increase sugar uptake by rat thymocytes is influenced by age and sex. In both sexes, T3 given in vitro stimulated sugar uptake in cells from animals of 15 days of age, had no effect at 21 days and was again effective at 26 days. In the male, thymocytes from animals of 40 days of age and older were refractory to T3. However, in the female, T3, although less effective than in cells from 26-day-old animals, remained stimulatory in cells from 40- and 60-day-old rats. T3 had no effect in cells from animals of 90 days of age and older. In in-vivo studies in which female rats of 26, 60 and 90 days of age were first injected with T3 and 1 h later with [3H]2-deoxyglucose, the responsiveness of thymocytes to T3 also declined progressively with advancing age; T3 was most effective in cells from 26-day-old animals, less stimulatory in 60-day-old and essentially without effect in cells from 90-day-old animals. From these observations we have concluded that in both male and female rats the responsiveness of thymocytes to T3 declines progressively with age, and that this decline occurs at an earlier age in cells obtained from males.

J. Endocr. (1986) 110, 511–515
Neonatal exposure to Δ9-tetrahydrocannabinol enhances sexual responses in the adult male mouse
Authors: Shrenker P. , Stegar R. , Bartke A.
Published: December 2008

From day 1 post partum to postnatal day 5, lactating female mice were given daily oral doses of 25 μl sesame oil, 0·5 mg tetrahydro-6,6,9-trimethyl-3-pentyl-6H-dibenzo(b,d)pyran-1-ol (Δ9-tetrahydrocannabinol; THC)/kg or 50 mg THC/kg in 25 μl oil. Additionally, the pups were given 20 μl oil, 10 μg testosterone or 20 μg testosterone in 20 μl oil s.c. from days 1 to 5 of age. This regimen resulted in nine treatment groups. At 60 days of age, all males were castrated and their testes weighed. After castration, each mouse was implanted s.c. with a 5 mm length of testosterone-filled silicone elastomer capsule. When adult they were tested for male copulatory behaviour. Following behavioural testing the animals were bled by cardiac puncture for measurement of plasma testosterone levels, and their hypothalami removed and assayed for dopamine, noradrenaline, 5-hydroxytryptamine (5-HT) and LH-releasing hormone (LHRH). In addition, another two groups of pregnant females were given daily oral doses of 0·5 or 50 mg THC/kg or oil during the first 3 or 5 days of lactation. The male pups were either decapitated for collection of trunk blood or homogenized for determination of serum or whole body testosterone concentrations. Neonatal administration of THC altered adult male sexual responses and had no effect on hypothalamic noradrenaline, 5-HT and LHRH concentrations. There were large increases in serum testosterone concentrations in neonates after maternal THC treatment, although these differences were not significant. Additionally, THC did not influence the testosterone content of neonatal tissue or the testosterone concentration of adult plasma.

These results suggest strongly that the effect of THC on male sexual responses is not mediated by its effect on adult hypothalamic neurotransmitter concentrations. Some other potential mechanisms are discussed.

J. Endocr. (1986) 110, 517–523