Adult baboons (5 males and 5 females) were exposed to immobilization stress by being strapped to a table in a horizontal position for 2 h. In females the experiment was performed during both the follicular and luteal phase. Peripheral blood was withdrawn at frequent intervals, the first sample just before immobilization, and the last one 3 days later. A number of steroids were measured in blood plasma samples by radioimmunoassay (17-hydroxypregnenolone, 17-hydroxyprogesterone, pregnenolone, testosterone, dihydrotestosterone, progesterone, 20α-dihydroprogesterone, oestrone, oestradiol) or competitive protein binding (cortisol) techniques.
The cortisol levels exhibited a marked increase in both sexes. This increase was observed already during the immobilization and lasted for approximately 24 h. A similar, even more pronounced increase was seen in 17-hydroxypregnenolone, 17-hydroxyprogesterone and pregnenolone levels. A marked, long-lasting (72 h) decrease of testosterone and dihydrotestosterone levels was a consistent finding in male baboons. This was not observed in the females which, on the other hand, exhibited a marked decrease (duration 48 h) of progesterone and 20α-dihydroprogesterone levels during the luteal phase, and a significant decrease (duration > 24 h) of oestradiol and oestrone concentrations during the follicular phase.
It is concluded that stress has a marked inhibitory action on gonadal function both in male and female baboons. In females the inhibition of steroidogenetic function is exerted both on the ovarian follicles and on the corpus luteum.
Effects of two (at 3 month interval) intramuscular injections of testosterone bucyclate (ТВ) in doses of 4 and 8 mg/kg b. w. were studied in adult male Papio hamadryas. Both ТВ doses suppressed spermatogenesis, but this effect abated with dose increase. Azoospermia was observed in 33% ejaculate samples after ТВ in a dose of 4 mg/kg, whereas after injection of 8 mg/kg it was found in only 6% samples. Moreover, the level of peripheral testosterone depends on ТВ dose as well. It reduces by half after injection of a lower dose and surpasses the control values by 20 to 120% after injection of 8 mg/kg. Time course of LH after injection of the androgen in both doses was characterized by a phase pattern: during the first phase (0 to 16 weeks) the levels of hormone varied, and a trend to reduction could be traced; during the second phase (weeks 16-24) the concentration of the hormone sharply increased and thus remained till the end of experiment. Prolonged exposure to long-acting ТВ may inhibit the secretion of adrenal androgen dehydroepiandrosterone and precursor of the ∆5-pathway of steroid synthesis 17-Oxypregnelone.
O. V Melnikova -RELATION SHIPS BETWEEN THE HYPOTHALAMO-PITUITARY-AD RENAL AND PEPTIDERGIC SYSTEMS OF THE HYPOTH ALAMUS IN ANIMALS WITH EXPERIMENTAL DIABETES MELLITUS Summary. The status of the hypollialamo-pituitary adre nal system (HPAS) and the group of regulatory neuropeptides synthesized iu the zone of the medial small cell hypothalamic subnticleus, the principal site of production of corticotropin re leasing factor, were studied in Wistar rats. HPAS was studied by radioimmunological and morphohistochemical methods, the neu ropeptidergic system by indirect immunofluorescence which helps measure the levels of neurotensin, bombesin, vasoactive intestinal peptide, leu-and mel-enkephalines, calcitonin-gene-related pep lide, and cholecystokinin in the neurones and medial eminence of the hypothalamus. Development of diabetes mellitus iu rats was found to be associated with an increase of HPAS activity and al teration of the peptidergic system presenting as an increase of the number of identified immunoreactive neurones and changed con tent of neuropeptides in neurones and of their concentration in the medial eminence.
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