Absence of feedback inhibition of prolactin secretion by the prostate

Previous observations in rodents and man have suggested the existence of feedback inhibition of pituitary prolactin secretion by the prostate. Thyrotrophin releasing hormone (TRH) tests performed in males before and after prostatectomy demonstrated no difference in prolactin or thyrotrophin (TSH) secretion. These data do not support the hypothesis of a prostate-pituitary feedback loop in the control of prolactin secretion. The results also imply that prostatic TRH acts in a paracrine manner.     

Effect of aromatizable androgens and estradiol on prolactin secretion in prepuberal male rats.

Intact and castrated male rats were injected daily for 10 days, beginning at 35 days of age, with either oil or one of the following steroids: testosterone propionate, dihydrotestosterone benzoate, androsterone acetate, androstenedione, androstandiol, or estradiol benzoate. Doses were 200 micrograms/rat/day for all androgens and 0.5 microgram or 2 micrograms/rat/day for estradiol. Significant increments in prolactin levels (fourfold over control values) in intact and castrated males were obtained after testosterone propionate and androstenedione treatment. Dihydrotestosterone, androsterone, and androstandiol did not induce any changes in either intact or castrated rats. Estradiol-treated males showed a four- and sevenfold increment in serum prolactin with the 0.5- and 2-microgram doses, respectively. These results suggest that androgens have a role in the control of prolactin secretion, particularly those that can be aromatized to estrogens by different tissues, including the hypothalamus.     

Pulsatile secretion of gonadotropins and prolactin in male marathon runners. Relation to the endogenous opiate system

We tested the hypothesis that sustained, strenuous physical training alters the neuroendocrine regulation of pulsatile gonadotropin and/or prolactin secretion in men. Blood was sampled at 20-minute intervals over 8 hours in five endurance-trained men after a 10-15 mile run in the middle of the active training season, and in 11 nonendurance trained normal controls. In these two groups, basal patterns of physiologically pulsatile secretion of LH, FSH, and prolactin (PRL) were not significantly different in relation to the following parameters: mean serum concentration of each of the three hormones (N = 25 samples); areas under the hormone concentration vs. time curves; fractional, incremental, and absolute pulse amplitudes; and pulse frequency, or periodicity. To test for enhanced suppressive effects of endogenous opiates in trained male marathon runners, subjects were administered the potent opiate-receptor antagonist, naltrexone (1 mg/kg). This antagonist significantly stimulated pulsatile LH secretion by increasing mean serum LH values from 10.94 to 13.58 mIU/ml (P = 0.007); area under the LH concentration vs. time curve increased from 5370 to 6510 mIU/ml X 8 hours (P = 0.05) and, pulse frequency rose from 2.8 to 4.9 pulses/8 hours (P = 0.006). Naltrexone also enhanced pulse frequency of FSH secretion from 3.4 to 5.4 pulses/8 hours (P = 0.009), but did not alter serum prolactin concentrations. None of these responses differed significantly from those in normal sedentary controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Spontaneous bacterial peritonitis in a healthy adult male

A 44-year-old man was admitted with acute abdominal pain, anorexia, nausea and dry retching, with tenderness and rigidity of the abdominal wall. Exploratory laparotomy revealed generalized peritonitis. He developed delerium tremens soon after operation and dehiscence of the abdominal wound 36 hours postoperatively. When the wound was closed and reinforced his recovery was uneventful. This case was unusual because he did not have ascites or cirrhosis, which are commonly associated with the disease.     

Effect of modulating endogenous prolactin secretion on testosterone production in the adult male bonnet monkey (Macaca radiata):

Adult male bonnet monkeys maintained under regulated light: dark conditions exhibit a nycthemeral surge of testosterone. The present study attempts to determine the effect of administration of drugs that modulate prolactin levels like ergobromocriptine (EBC) and chlorpromazine (CPZ) on testosterone production. The injection of EBC, a known inhibitor of prolactin secretion, could abolish nocturnal testosterone surge irrespective of the drug being given at 8.00 or 17.00 h. Testosterone surge could likewise be inhibited by treating animals with CPZ, a potent stimulator of prolactin secretion. This suggests that alteration in endogenous prolactin level from the normal effects nycthemeral surges of testosterone. The in vivo responsiveness of the testes of monkeys injected either CPZ oder EBC to exogenous LH or LHRH stimulation was tested. While LH could completely override the CPZ induced inhibition in testosterone production it could only partially reverse the EBC effect.     

Zygodactyly with thumb aplasia: an unusual variant in a male subject

This is a presentation of a male subject with unusual combination of limb malformations. The subject had unilateral zygodactyly of the left foot with thumb aplasia in the right hand. Further, the webbing between second and third toes was complete culminating in osseous fusion of the terminal phalanges and valgus deviation of the affected digits of the foot. The nails were also involved but had separate origins. In the right hand, first digital ray was observed to be completely omitted. There was aplasia of certain carpals while the radius showed minimal clinical symptoms. The subject was the product of first cousins union. To the best of our knowledge, this combination of limb phenotype has not been described before.     

Insulin secretion in healthy Indian volunteers

The insulin response to a 100 g oral glucose load was studied in 20 non-obese, healthy Indian females and 20 matched Indian males. There were no differences between the mean glucose responses of the two groups. However, early-phase (0-60 minutes) insulin release was significantly greater in the females. While there were no significant differences between the two groups when the total areas under the insulin and glucose curves were computed, the female volunteers had a significantly higher mean insulinogenic index. It therefore appears that healthy Indian females have significantly greater early-phase insulin release than their matched male counterparts.     

The role of prolactin in the pathogenesis of male sterility

To study the causal relationship between the hormonal status and spermatographic data in sterile males, the authors investigated the correlations between the plasma levels of testosterone, estradiol, prolactin and gonadotrophin and certain parameters of spermograms and computed the correlative relationship of those values. The findings demonstrated the increased levels of prolactin (249.09 +/- 39.6 mu/U/ml), significantly exceeding the normal (132.6 +/- 32.4 mu/U/ml), a tendency towards a decrease in the levels of FSH and testosterone (up to 7.01 +/- 0.70 nmol/l versus 12.57 +/- 0.39 nmol/l in health) and manifest elevation of estradiol levels (up to 634.71 +/- 29.16 nmol/l versus 205.02 +/- 18.60 nmol/l), as well as its ratio to the testosterone levels. The number of spermatozoa in 1 ml was found decreased up to 29.6 +/- 4.10 million, the volume of ejaculate was reduced to 2.7 +/- 0.41 ml, while the percentage of immobile spermatozoa rose to 40.00 +/- 4.76. Despite of some pathological changes evidenced by spermograms, there was the only parameter--the volume of ejaculate--that was directly dependent on the levels of prolactin, their correlation was reversed. Decreased numbers of spermatozoa and their motility were not related to hyperprolactinemia. Moreover, there was a positive correlation between the levels of prolactin and the motility of spermatozoa in sterile patients. Therefore, decreased number and motility of spermatozoa turned to be dependent not on prolactin but sex hormone levels. However, ejaculation was found unfeasible in male with high levels of hyperprolactinemia.     

Pharmacokinetics of dopamine in healthy male subjects

BACKGROUND: Dopamine is an agonist of alpha, beta, and dopaminergic receptors with varying hemodynamic effects depending on the dose of drug being administered. The purpose of this study was to measure plasma concentrations of dopamine in a homogeneous group of healthy male subjects to develop a pharmacokinetic model for the drug. Our hypothesis was that dopamine concentrations can be predicted from the infusion dose using a population-based pharmacokinetic model. METHODS: Nine healthy male volunteers aged 23 to 45 yr were studied in a clinical research facility within our academic medical center. After placement of venous and arterial catheters, dopamine was infused at 10 microg x kg(-1) x min(-1) for 10 min, followed by a 30-min washout period. Subsequently, dopamine was infused at 3 microg x kg(-1) x min(-1) for 90 min, followed by another 30-min washout period. Timed arterial blood samples were centrifuged, and the plasma was analyzed by high-performance liquid chromatography. Mixed-effects pharmacokinetic models using NONMEM software (NONMEM Project Group, University of California, San Francisco, CA) were used to determine the optimal compartmental pharmacokinetic model for dopamine. RESULTS: Plasma concentrations of dopamine varied from 12,300 to 201,500 ng/l after 10 min of dopamine infusion at 10 microg x kg(-1) x min(-1). Similarly, steady-state dopamine concentrations varied from 1,880 to 18,300 ng/l in these same subjects receiving 3-microg x kg(-1) x min(-1) infusions for 90 min. A two-compartment model adjusted for body weight was the best model based on the Schwartz-Bayesian criterion. CONCLUSIONS: Despite a homogeneous population of healthy male subjects and weight-based dosing, there was 10- to 75-fold intersubject variability in plasma dopamine concentrations, making standard pharmacokinetic modeling of less utility than for other drugs. The data suggest marked intraindividual and interindividual variability in dopamine distribution and/or metabolism. Thus, plasma dopamine concentrations in patients receiving dopamine infusion at identical rates may vary profoundly. Our data suggest that dosing dopamine based on body weight does not yield predictable blood concentrations.     

Absence of Goodpasture's antigen in male patients with familial nephritis

The presence of Goodpasture's (GP) antigen in the glomerular basement membrane (GBM) of the kidney was evaluated by indirect immunofluorescence in nine patients with familial nephritis from five kindreds. The GP antigen was not detected in seven males but was present in an affected sister and mother, an unaffected brother, and 13 normal controls. The specificity of this finding in affected males is supported by the persistence of other GBM antigens identified by monoclonal antibodies. The lack of GP antigen in affected males and its persistence in related females with the disease suggests a possible X-linked dominant mode of inheritance. We propose that the absence of GP antigen leads to severe disease in the male, whereas its presence in related females is associated with mild disease.