Renin in the rat pituitary coexists with angiotensin II and depends on testosterone.

In the rat pituitary gland, immunoreactive angiotensin II (ANG II), renin, and LH, but not PRL, were found within the same cells of the anterior pituitary gland by staining with the avidin-biotin complex method in adjacent sections. No renin-positive staining was observed in the pituitary of the rats after 10 days of castration, but positive staining reappeared after 8 weeks. This effect of castration on renin immunoreactivity was abolished by the simultaneous administration of testosterone. In contrast, ANG II immunoreactivity was unaffected by castration. The intensity of renin immunoreactivity in the pituitary was less prominent in the female than in the male rat. These results suggest that there exists a pituitary renin-angiotensin system localized in the gonadotrophs and that the pituitary renin is under androgenic control.

C-type natriuretic peptide as a possible local modulator of aldosterone secretion in bovine adrenal zona glomerulosa.

Although atrial and brain natriuretic peptides are well known to be involved in the regulation of cardiovascular and endocrine functions as circulating hormones, the roles of the C-type natriuretic peptide (CNP) remain unknown. We examined the effects of CNP on the secretion of aldosterone and cyclic nucleotides from bovine adrenal zona glomerulosa cells in culture. CNP produced a dose-dependent increase in the basal secretion of cGMP, with an EC50 of 3.8 x 10(-10)M. CNP significantly inhibited the ACTH-induced increase in aldosterone and cAMP in a dose-related manner, with an IC50 of 3.6 x 10(-10)M. Although ACTH itself did not increase cGMP secretion, the addition of CNP elicited a significant increase in cGMP secretion. The effects of CNP on the basal secretion of cGMP and the ACTH-induced secretion of aldosterone were significantly reversed by a nonpeptide natriuretic peptide receptor antagonist, HS-142-1. CNP immunoreactivity was localized in the zona glomerulosa by immunohistochemical staining. In addition, expression of CNP messenger RNA and natriuretic peptide B receptor messenger RNA was demonstrated by RT-PCR in the zona glomerulosa tissue and cells in culture. These findings suggest that CNP is a local factor regulating ACTH-induced aldosterone secretion through a guanylyl cyclase-cGMP pathway.

FSH and LH secreting pituitary adenoma.

A case of FSH and LH secreting pituitary adenoma which was not preceded by hypogonadism is reported. The patient, a 50-year-old man, was admitted to the hospital because of left temporal hemianopsia. No clinical evidence of hypogonadism was demonstrated. Endocrine studies of hypogonadism was demonstrated. Endocrine studies revealed markedly elevated plasma FSH of 295 mIU/ml and slightly elevated LH of 35 mIU/ml (2nd IRP-HMG). Plasma FSH and LH did not respond to the administration of LRF, conjugated equine estrogens and testosterone. Plasma testosterone was 691 ng/dl and rose nromally after pregnant mare's serum gonadotropin. Sperm count was 46 X 10(6)/ml. Transfrontal hypophysectomy was followed by a marked decrease of both FSH (to 19mIU/ml) and LH (to 22 mIU/ml). Histologic examination of the tumor revealed 90% chromophobe cells and 10% slightly eosinophilic cells. Two sizes of secretory granules were demonstrated. Tumor cells in tissue culture secreted both FSH and LH.

Prolactin directly inhibits basal as well as gonadotropin-stimulated secretion of progesterone and 17 beta-estradiol in the human ovary.

An ovarian perifusion technique was used to determine if there is a direct suppressive effect of PRL on human gonadal steroid secretion. Ovarian tissue from nine patients was examined. Ovine PRL (0.1-10 IU/ml) directly suppressed progesterone and 17 beta-estradiol secretion by human ovaries. hCG (1-10 IU/ml) stimulated both progesterone and 17 beta-estradiol secretion. Simultaneous administration of PRL (5-10 IU/ml) suppressed the stimulatory effect of hCG. The ovarian tissue obtained from a hyperprolactinemic patient did not respond to hCG. These results indicate that PRL inhibits both basal and gonadotropin-stimulated ovarian steroid secretion by human ovaries and that this may be one cause of the hypogonadism associated with hyperprolactinemia.

Corticotropin-releasing factor-like activity in ACTH producing tumors.

Corticotropin-releasing factor (CRF)-like activity in two different kinds of ACTH-producing tumors (human ectopic ACTH-producing colonic cancer and rat MtT/F4 tumor) was determined by an in vitro method using isolated normal rat pituitary cells. The ACTH content of the post mortem colonic cancer was 5.5 ng/g w.wt. The ACTH content of the medium of MtT/F4 tumor cells was 153+/-32 pg/10(5) cells. The ACTH content of MtT/F4 tumor cell suspensions was elevated with increasing doses of hypothalamic median eminence extract (HME). The response of MtT/F4 tumor cells to HME was suppressed by 1 mug/ml of dexamethasone. Extracts of colonic cancer, MtT/F4 tumor and HME produced elevation of the ACTH content of the medium of isolated rat pituitary cells. The CRF-like activities of two kinds of tumor extracts in multiple dilutions ran parallel to that of HME. The CRF-like activities were 0.037 HME equiv/mg w.wt in MtT/F4 tumor and 0.052 HME equiv/mg w.wt. in colonic cancer. These results demonstrated that CRF-like activity existed in these two kinds of ACTH-producing tumors.

Endothelin-3 immunoreactivity in gonadotrophs of the human anterior pituitary.

Endothelin (ET), originally discovered in vascular endothelial cells, has also been demonstrated in nonvascular tissues. The present study was undertaken to elucidate the presence of ET in the human pituitary. The avidin-biotin complex method with antiserum to ET-1 (and ET-2) or ET-3 was used to identify ET in human pituitaries obtained by autopsy. ET-3 immunoreactivity was found in the cytoplasm of large ovoid cells of the anterior pituitary. Using the double staining method, the cells containing ET-3 immunoreactivity were differentiated from cells containing ACTH, TSH beta, GH, PRL, and protein S-100. By staining with anti-LH beta antiserum in adjacent sections and using the double staining method, the cells were identified as gonadotrophs. No staining was observed in the posterior pituitary. In addition, no ET-1 (and ET-2) immunoreactivity was detected. The specific localization of ET-3 immunoreactivity in the gonadotrophs of the human pituitary suggests a possible role of ET-3 in the regulation of anterior pituitary function.

Failure of naloxone to influence plasma growth hormone, prolactin, and cortisol secretions induced by insulin hypoglycemia.

The effect of naloxone, a specific antagonist of opioid peptides, on plasma, GH, PRL, and cortisol responses to insulin-induced hypoglycemia was studied in five healthy male subjects. The iv administration of regular insulin (0.15 U/kg) led to similar degrees of hypoglycemia on control and experimental days. Plasma GH, PRL, and cortisol levels rose significantly in response to insulin-induced hypoglycemia. A 2-h infusion of naloxone (0.8 mg/h) started 30 min before insulin injection did not alter either basal hormone levels or the hormone responses to insulin-induced hypoglycemia. These results suggest that endogenous opioid peptides do not play a major role in GH, PRL, or cortisol secretion induced by insulin hypoglycemia.

Plasma pituitary hormone responses to the synthetic enkephalin analog (FK 33-824) in normal subjects and patients with pituitary diseases.

D-Ala, Mephe, Met, enkephalin (Sandoz FK 33-824) is a stable long acting analog of methionine-enkephalin. FK 33-824 (0.5 or 1.0 mg), elicited plasma GH and PRL responses in normal subjects. In 23 patients with pituitary dwarfism, the response of plasma GH was markedly impaired, while PRL responded to a variable degree. In patients with acromegaly, there was little or no increase in GH and PRL after FK 33-824. Plasma GH increased to a variable degree after FK 33-824 in patients with hyperprolactinemia, with little change in plasma PRL. FK 33-824 decreased plasma cortisol in normal subjects and patients with pituitary disease. These results show that patients with acromegaly and hyperprolactinemia due to pituitary adenomas and patients with pituitary dwarfism do not respond well to FK 33-824, presumably because of hypothalamic or pituitary derangement.

Falsely elevated serum parathyroid hormone levels due to immunoglobulin G in a patient with idiopathic hypoparathyroidism.

A 73-yr-old patient with idiopathic hypoparathyroidism was admitted to our hospital in May 1981. The immunoreactive PTH (iPTH) level determined by RIA using antiserum specific for the C-terminal region of PTH-(65-69) was in the upper normal range (0.6 ng/mL) and over the next 7 yr increased gradually to 6 ng/mL. Since iPTH levels determined using other commercial RIA kits remained constantly decreased or in the undetectable range, we studied the mechanism of false elevation of iPTH in this patient. The patient's serum contained no binding protein to the tracer ([125I]) [Tyr45] human PTH-(46-84)), nor was any heterophilic antibody to the first [guinea pig immunoglobulin G (IgG)] or the second antibody (goat IgG) detected. Consistent with these findings, the dilution curve of the serum was parallel with that of standard bovine PTH-(1-84). Gel filtration analysis revealed that the iPTH-like substance was eluted in the void volume (apparent mol wt, greater than 70,000). Almost all of the iPTH-like substance was adsorbod by a protein-A-Sepharose column. When the IgG fraction purified by protein-A-Sepharose affinity chromatography was applied to an antihuman IgG lambda-Sepharose column, 72% of the iPTH-like substance was detected in the IgG lambda. These results suggest that the falsely elevated iPTH in the patient's serum was due to IgGs (mainly IgG lambda), which were cross-reactive with the antiserum highly specific for the C-terminal region of human PTH-(65-69).

ACTH, beta-LPH and beta-endorphin in pituitary adenomas of the patients with Cushing's disease: activation of beta-LPH conversion to beta-endorphin.

ACTH, beta-lipotropin (beta-LPH) and beta-endorphin concentrations were determined in pituitary adenomas of the patients with Cushing's disease. Immunoreactive ACTH and beta-endorphin were present in high concentrations and essentially equimolar amounts in pituitary adenomas. beta-LPH conversion to beta-endorphin was activated in pituitaries associated with ACTH/beta-LPH producing adenomas. Immunoreactive ACTH and beta-endorphin concentrations were markedly suppressed in the surrounding tissues.

Human plasma free activin and inhibin levels during the menstrual cycle.

The role of inhibin in gonadal function and reproduction has been confirmed by the measurement of plasma inhibin levels, but there has been no clinical data available on activin because of the lack of a good assay method. We measured plasma free activin levels during the normal menstrual cycle using a newly developed competitive protein binding assay with follistatin as the binding protein. Plasma inhibin levels were measured simultaneously using an alpha-subunit N-terminal fragment RIA with recombinant inhibin as the reference standard. Four normal women, aged 23-29 years, were investigated by obtaining plasma at 3-day intervals. Plasma inhibin levels showed some variation during the follicular phase, but a parallel rise in inhibin and progesterone was observed during the luteal phase. These findings confirmed those of previous studies. In contrast, plasma free activin levels did not show any substantial changes during the menstrual cycle. This study suggests that activin has no endocrine role in modulating the pituitary-gonadal axis during the normal menstrual cycle, while changes of inhibin reflect cyclic gonadal function and indicate an endocrine role for this protein in modulating gonadal activity.

Anterior pituitary hormones in plasma and pituitaries from patients with Cushing's disease.

Pituitary adenomas were obtained from eight of nine patients with Cushing's disease, and the surrounding tissues as well were obtained from six of nine patients. ACTH, beta-lipotropin (beta-LPH), beta-endorphin, GH, TSH, LH, and PRL concentrations in these tissues were determined by RIA. Immunoreactive ACTH and beta-endorphin (beta-endorphin + beta-LPH) were present in high concentrations in all adenomas, and low concentrations were found in the surrounding tissues, except for one patient. As compared to levels seen in normal pituitary tissue, the GH concentration in the surrounding tissues was suppressed in five of six cases. TSH and LH concentrations were suppressed in four and three cases, respectively. The PRL concentration was not suppressed in any of the six patients studied. These four hormones were not detected in any adenoma. Plasma GH, TSH, and LH responses to various stimuli which were suppressed preoperatively returned to normal in most of the patients after adenomectomy. Basal plasma cortisol concentrations were normal or subnormal and were suppressed by the administration of 1 mg dexamethasone after adenomectomy, in contrast to the lack of such suppression preoperatively. ACTH and beta-endorphin secretion were stimulated by lysine-8-vasopressin and suppressed by dexamethasone and cyproheptadine in vitro.

The significance of alpha-subunit as a tumor marker for gonadotropin-producing pituitary adenomas.

We studied gonadotropin hormone alpha-subunit and gonadotropin secretion in four patients with gonadotropin-producing pituitary adenomas. All four patients had elevated plasma alpha-subunit levels, ranging from 2.8-8.5 ng/ml (normal, less than 0.5 ng/ml). alpha-Subunit responses to LHRH were less than those in seven patients with primary gonadal failure. The relative proportions of the gonadotropin and alpha-subunit peaks in one patient were the same before and after LHRH administration, based on gel filtration studies of plasma. The alpha-subunit levels decreased little during testosterone treatment in the two adenoma patients so treated. Immunohistochemical study of the adenomas from two patients demonstrated definite staining with alpha-subunit and gonadotropin antisera. Elevated plasma levels of alpha-subunit and its relative unresponsiveness to LHRH stimulation or testosterone suppression suggest that the alpha-subunit originated in tumor tissue and that its measurement is useful for the diagnosis of a gonadotropin-producing tumor in patients with elevated plasma levels of LH and/or FSH.

Effects of two calcium channel blockers on messenger RNA expression of endothelin-1 and nitric oxide synthase in cardiovascular tissue of hypertensive rats.

OBJECTIVE: The aim of this study was to investigate the effects of calcium channel blockers on messenger RNA expression of endothelin-1 and endothelial-type nitric oxide synthase in the cardiovascular tissue of stroke-prone spontaneously hypertensive rats (SHRSP). MATERIALS AND METHODS: The calcium channel blocker nilvadipine (1.0 or 3.2 mg/kg per day) was subcutaneously administered to two groups of SHRSP, from 4 or 8 weeks of age, for 8 weeks and 4 weeks, respectively. For comparison, nifedipine (3.2 mg/kg per day) was similarly administered to SHRSP from 4 weeks of age for 8 weeks. Kidney, heart, aorta and brain tissue samples were obtained when the rats were 12 weeks old. Messenger RNA expression of endothelin-1 and endothelial-type nitric oxide synthase was determined by reverse transcription-polymerase chain reaction followed by Southern blotting and a ribonuclease protection assay, respectively. Results were compared with those in untreated SHRSP and Wistar-Kyoto rats at 12 weeks of age. RESULTS: Both nilvadipine and nifedipine significantly decreased blood pressure in SHRSP. Although there were no changes in the weights of the kidney and brain, there was a significant decrease in the weight of the left ventricle of the groups treated with nilvadipine (1.0 mg/kg per day: mean +/- SEM 0.282 +/- 0.003 g; 3.2 mg/kg per day: 0.269 +/- 0.005 g) and nifedipine (1 mg/kg/day: 0.281 +/- 0.012 g) for 8 weeks compared with untreated SHRSP (0.301 +/- 0.004 g). Endothelin-1 messenger RNA expression, which was significantly increased by about twofold in the kidney, heart and brain of SHRSP compared with Wistar-Kyoto rats, was normalized by both calcium blockers. Endothelin-1 messenger RNA expression, which was decreased in the aorta of SHRSP, was further decreased by both calcium blockers. While there was no significant difference in endothelial-type nitric oxide synthase messenger RNA expression in the kidney, heart and aorta between the untreated SHRSP and Wistar-Kyoto rats, expression in the aorta was significantly increased in the group treated with these calcium blockers for 8 weeks from 4 weeks of age. CONCLUSIONS: These results suggest that, in addition to their potent antihypertensive effects, calcium channel blockers may exhibit cardiovasculoprotective and renoprotective effects by modifying mRNA expression of endothelin-1 and endothelial-type nitric oxide synthase in tissue.

Left ventricular hypertrophy is more prominent in patients with primary aldosteronism than in patients with other types of secondary hypertension.

We determined functional and morphological changes of the heart by 2-dimensional and pulse Doppler echocardiography in 20 patients with primary aldosteronism and compared the results with those in 50 healthy normotensive subjects, 12 patients with Cushing's syndrome, 9 patients with pheochromocytoma, and 47 patients with essential hypertension. All hypertensive groups had greater left ventricular mass indexes than did the normotensive group (76.9 +/- 17.2 g/m2). Despite similar age distribution, blood pressure during antihypertensive treatment, and duration of hypertension, the primary aldosteronism group had a significantly greater left ventricular mass index (152.5 +/- 42.5 g/m2) than did the Cushing's syndrome (103.4 +/- 37.5 g/m2), pheochromocytoma (122.4 +/- 28.5 g/m2), and essential hypertension (101.4 +/- 32.8 g/m2) groups. The left ventricular posterior wall thickness and interventricular septal wall thickness were significantly greater in the hypertensive groups than in the normotensive group and also significantly greater in the primary aldosteronism group than in any of the other hypertensive groups. By contrast, there were no significant differences among the four hypertensive groups in any variable of systolic or diastolic function of the heart. The results suggest that left ventricular hypertrophy is more pronounced in patients with primary aldosteronism than in patients with other forms of hypertension. It is therefore important to echocardiographically evaluate cardiac hypertrophy as a risk factor of morbidity and mortality in patients with this low renin hypertension.

Dopaminergic regulation of aldosterone secretion: its pathophysiologic significance in subsets of primary aldosteronism.

Although aldosterone (Aldo.) secretion is regulated by various humoral factors, evidence has accumulated to support an involvement of dopaminergic system in its regulation. The pathophysiological significance of the dopaminergic system in primary aldosteronism (PA) however remains unknown. In the present study, we examined the effects of metoclopramide (MCP) on Aldo. secretion in normal subjects (n = 11) and patients with essential hypertension (EH, n = 8), aldosterone-producing adenoma (APA, n = 10), and idiopathic hyperaldosteronism (IHA, n = 6). Plasma Aldo., prolactin (PRL), renin, cortisol, serum sodium, and serum potassium levels were determined before and 30 min after i.v. bolus injection of 10 mg MCP at 9 a.m. Plasma Aldo. showed a significant increase after MCP in normal subjects, EH, and APA, but not in IHA. The incremental response of plasma Aldo. was largest in APA and smallest in IHA. The percentage increase in plasma Aldo. from the basal level was significantly attenuated in IHA, while no significant difference was seen among other groups. Although plasma PRL showed a significant increase in response to MCP, no difference of the change was seen among the groups. There was no significant change in plasma cortisol, renin, serum sodium, and serum potassium levels in response to MCP. In addition, the response of Aldo. to MCP was normalized in APA after unilateral adrenalectomy, while that of PRL did not change. These results indicate that the adrenal dopaminergic activity is enhanced in APA and attenuated in IHA and suggest an involvement of the dopaminergic system in the pathogenesis of IHA.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of immobilization stress on testosterone and inhibin in male rats.

Adult male Wistar rats were subjected to acute and chronic immobilization stress. Changes in plasma levels of LH, FSH and testosterone and in the content of testicular inhibin and testosterone were studied. Plasma LH levels decreased significantly in response to both acute and chronic stress. Significant decreases in plasma testosterone content were also observed after chronic stress. In contrast, plasma FSH and testicular bioassayable inhibin content did not change after acute or chronic stress. These findings indicate that in male rats immobilization stress induced a dissociation in LH and FSH responses, and decreased testosterone while inhibin remained unaffected.

Human chorionic gonadotropin produced by ectopic pinealoma in a girl with precocious puberty. Case report.

A case is reported in which a human chorionic gonadotropin (HCG-)-producing ectopic pinealoma was found in a 5-year-old girl with precocious puberty. Physical examination revealed abnormal breast enlargement. Endocrinological study disclosed a high plasma HCG concentration of 1192 ng/ml with a normal follicular stimulating hormone (FSH) level. The HCG content of the tumor was as high as 400 ng/mg of acetone dried tissue, but no FSH was detectable. This is the first reported case of precocious puberty associated with pineal tumor in a female.

Induction of heme oxygenase produces load-independent cardioprotective effects in hypertensive rats.

Although heme oxygenase (HO) has been suggested to be involved in the regulation of cardiovascular function through production of carbon monoxide (CO), the pathophysiological significance of HO in hypertensive organ damage remains unknown. We examined the effects of inducing HO-1 mRNA by stannous chloride (SnCl2) on cardiac hypertrophy in stroke-prone spontaneously hypertensive rats (SHR-SP/Izm). Chronic administration of SnCl2 resulted in a significant decrease in left ventricular (LV) weight/body weight ratio and LV brain natriuretic peptide (BNP) mRNA levels as a marker of cardiac hypertrophy and a significant increase in LV HO-1 mRNA levels and LV cGMP contents in SHR-SP/Izm, while there was no significant change in systemic blood pressure. These results provide the first evidence that induction of HO in the heart attenuates cardiac hypertrophy in load-independent mechanism in genetically hypertensive rats.

Deferential roles of angiotensin receptor subtypes in adrenocortical function in mice.

The functional significance of angiotensin II (Ang II) receptor subtypes in adrenals remains unknown. Ang II receptor type 1a (AT1a) expression was localized by in situ hybridization to the zona glomerulosa and zona fasciculata, while AT1b was localized to the zona glomerulosa. Plasma aldosterone and corticosterone levels were measured after injection with Ang II or the type 2 receptor (AT2) agonist CGP-42112 in wild-type and AT1a deficient mice. Aldosterone and corticosterone levels were lower in AT1a deficient mice. Ang II increased plasma aldosterone levels in AT1a deficient mice, but to a lesser extent in mice pretreated with nonselective AT1a/AT1b antagonist, CV-11974. CGP-42112 did not affect aldosterone levels. Ang II increased corticosterone levels in wild-type mice but not in AT1a deficient mice. Results suggest Ang II stimulates aldosterone secretion via AT1a and AT1b in the zona glomerulosa and corticosterone secretion via AT1a in the zona fasciculata, and provide first evidence for differential roles of AT1a and AT1b in the adrenals.