Plasma testosterone response to repeated human chorionic gonadotropin administration is increased in trained athletes.

In a group of 34 athletes and 11 untrained volunteers the plasma testosterone response to human chorionic gonadotropin (hCG) stimulation was evaluated. The hCG stimulation tests were performed by injecting 3000 IU of hCG i.m. on three consecutive days with plasma testosterone determinations before the first injection and 24 h after the last, i.e. third hCG injection. The basal testosterone levels were similar in both trained and untrained individuals. Plasma testosterone levels in response to repeated hCG stimulation were found to be significantly higher in the group of trained subjects.

Hypertension induced by repeated stress: possible participation of sympathetic-adrenomedullary catecholamines.

Several groups of male Wistar rats weighing 250-300 g were subjected to immobilization stress (IMO) for various intervals (2.5 h to 19 h daily omitting weekends for a total of 2 to 15 weeks). Blood pressure (BP) was measured with the aid of indirect cuff pressure method under routine conditions once weekly during the whole period of immobilization and in some groups also for 10 weeks after the end of this period. It was found that BP significantly increased after 2 weeks of 2.5 h IMO daily and progressively increased later on. There was an indirect relationship between the duration on individual intervals of IMO and the period which was necessary to develop a significant increase of BP. Adrenal medullectomized animals showed a significantly less increase of BP than normal ones during 16 weeks course of IMO. The level of adrenaline and noradrenaline was significantly increased in animals having 24-hour rest after 39th IMO compared to controls, the blood being taken by chronically implanted cannula in a tail artery.

Plasma testosterone during bicycle ergometer exercise without and after L-dopa pretreatment.

The level of testosterone in plasma during submaximal, prolonged submaximal and maximal exercise on a bicycle ergometer was measured in healthy untrained men. To evaluate the possible involvement of prolactin in the regulation of testosterone secretion during exercise, the influence of prolactin inhibition by oral L-dopa (1 g) pretreatment was also studied. The exercise evoked a small but significant rise of testosterone concentration with peak levels immediately at the end of work performance or 10 min after that. No substantial difference between the response to submaximal and maximal exercise was noted. In these experiments the findings by others on a lack of plasma LH changes and significant increase of plasma prolactin were confirmed. Pharmacological blockade of prolactin release by L-dopa pretreatment failed to modify the response of testosterone to bicycle ergometer exercise. It may be suggested that prolactin is not involved in the induction of plasma testosterone increase during physical exercise.

Plasma testosterone response to HCG in normal men without and after administration of anabolic drug.

In young, adult male volunteers Leydig cell function tests were performed consisting of i.m. administration of 1500, 3000 or 4500 IU of HCG on days 1, 2 and 3 and plasma testosterone determination by radioimmunoassay. The stimulatory effect of HCG known from the literature is reconfirmed. However, no difference between the effect of the three dosage levels was found and the first significant effect of HCG was observed 24 h after its first application. Testosterone levels on day 3 and 4 are higher but not different from each other. A depression of plasma testosterone after treatment with an anabolic steroid (1alpha, 17alpha-dimethyl-5alpha-androstan-17-ol-3-one) 20 mg daily for 14 days is described. Reactivity to HCG was sustained in these subjects, but testosterone response to HCG was diminished at all investigated time intervals.

Catecholamines in individual hypothalamic nuclei of acutely and repeatedly stressed rats.

Norepinephrine (NE) and dopamine (DA) concentrations in 17 individual hypothalamic nuclei and 3 other brain regions were measured in rats, acutely or repeatedly stressed by immobilization, using a microdissection technique and a radioisotopic-enzymatic assay. Following the first 20 min immobilization (IMO) a significant NE decrease in the ventromedial (NVM) and supraoptic (NSO) nuclei and a DA decrease in the arcuate nucleus (NA) as well as NE and DA increase in the dorsomedial nucleus (NDM) were seen. Repeated IMO (40 times) produced a NE increase in the NVM, NDM, NSO paraventricular nucleus (NPV) and median eminence (ME), and a DA increase in the NDM and NPV. Changes of NE and DA concentration found in some individual hypothalamic nuclei under the influence of stress indicate that catecholamines (CAs), particularly in the medial basal hypothalamus, could be involved in the regulation of some neuroendocrine processes which are being activated during stress, especially ACTH release.

Plasma testosterone of rats subjected to immobilization stress and/or HCG administration.

The effect of immobilization stress (IMO) on the plasma testosterone level in rats has been investigated. Plasma testosterone was not changed after 10 or 20 min IMO for 3 consecutive days as compared to nonstressed animals and the 10-min trial was without effect even if it was applied daily for 42 days. Thre days IMO for 60 min caused a significant hormone decrease, which was even more pronounced after 3 or 42 days IMO for 120 min. The administration of HCG to rrats immobilized 3 days for 120 min resulted in the increase of testosterone, however, the final level was significantly lower in comparison to nonstressed controls.

Effect of clomiphene citrate on PMSG-induced ovulation in the immature rat.

The dose of 15 IU PMSG was found to be optimal for inducing ovulation within 74 hours in 27-day-old immature female rats. There was a significant decrease in the mean number of ova per ovulating animal when the dose was raised beyond this (r = 0.6554, p less than 0.001 for the range from 15 to 100 IU), but the number of ovulating animals did not decrease unless more than 80 IU PMSG were injected. The PMSG-induced ovulation was not affected by treating the animals with 10 or 100 mug clomiphene citrate at 0, 24, 48, 54, 60, 66 hours or at 0, 24, and 48 hours.

PIP: The effect of clomiphene citrate (10 or 100 mcg) treatment on ovulation induced by pregnant mares' serum gonadotropin (PMSG) was studied in 27-day-old female rats. It was found that 15 IU PMSG was optimal for inducing ovulation within 74 hours of treatment. When the dose was increased beyond 80 IU, the number of ovulating animals significantly (p less than .01) decreased. The mean number of ova per ovulating animal was also decreased by doses greater than 15 IU. Treatment with clomiphene, at either dose, at 0, 24, 48, 54, 60, and 66 hours did not affect PMSG-induced ovulation.