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Experiments were performed in castrated adult male and female rats of the Sprague-Dawley strain (Charles River, Italia). Animals (150-170 g) were castrated under light ether

Summary. The effect of 5a-androstan-17fl-ol-3-one (DHT) and of 5a-androstan-3a, 17fl-di01 (3a-dioi) on stress-induced prolactin hypersecretion has been investigated in castrated female rats. A 6-day treatment with 2 mg of these steroids does not inhibit the ether-induced increase in prolactin serum levels.Data obtained in this and other laboratories indicate that testosterone is converted in the brain (mainly in the hypothalamus) and in the anterior pituitary into a series of 5a-reduced metabolites. Among these the most prominent ones appear to be 5a-androstan-17/~-ol-3-one (dihydrotestosterone, DHT), 5a-androstan-3a,17fl-diol (3a-diol) and 5a-androstan-3fl,17fl-diol (3fl-diol) 1. Very little information is available on the effects of these metabolites of testosterone on prolactin secretion z-5. In previous work it has been shown that DHT and 3a-diol (but not 3fl-diol) when given for 6 days at the doses of 2 mg/rat/day may inhibit prolactin secretion in long-term castrated female rats in resting conditions 6. This effect appears to be at variance with that of testosterone. This steroid has been reported by several authors either to stimulate or not to affect prolactin release 2,7-12. It has been repeatedly reported that a variety of stresses enhance prolactin secretion in the rat 13-1s. The present experiments have been performed in order to analyze whether DHT and 3a-diol might counteract the stimulatory effect of stress on prolactin secretion. Adult female Sprague-Dawley rats (Nossan, Italy) were castrated under light ether anesthesia 5 weeks before starting the experiment. The experimental groups were pretreated for 6 days with 2 mg/day of DHT or 3a-diol (Sigma, St.Louis). The steroids were injected s.c. in 0.2 ml of peanut oil. The same amount of oil was injected in 2 of the 4 control groups (oil controls non-stressed and oil controls ether-stressed). Since the 2 remaining groups of controls (controls non-stressed, controls ether-stressed) did not receive any treatment, they were handled each day for a few minutes. Stress consisted of the exposition to ether vapor for 2 min. After the application of stress, the animals were individually caged, Effect of DHT and 3a-diol (2 mg/rat s.c. for 6 days) on serum prolactin levels in long term castrated female rats exposed for 2 min to ether vapors. Blood was collected 15, 30, 45 min after the end of stress ng/ml RP-2 Values are means+ SEM. Number of animals in parenthesis. * Significant p<0.05 vs non-stressed; ** Significant p<0.05 vs non-stresses + oil.in a silent room. and killed with a guillotine within 30 sec after removal from the cage. The same care to avoid handling and noise stresses was given to the control nonstressed animals. Blood was collected 14, 30 and 45 rain after the end of ether application. Proiactin levels were determined by a specific RIA method 16. RIA calculations were performed utilizing a Digital-Minc-11 computer connected on line with the counters. The logit-log transformation was used for the interrelation On the standard curve 17. The da...

The oestrogenic activity of cyclophenil, a non-steroidal compound which has structural analogies with both stilbene and triphenylethylene, has been reevaluated utilizing both central and peripheral parameters. The central parameters considered were LH, FSH, prolactin secretion and two enzymatic systems known to be oestrogen-sensitive: hypophyseal 5\g=a\-reductase and hypothalamic aromatase. The uterine growth test was used to determine oestrogenic peripheral activity. The compound was administered at various doses in comparison with oestradiol benzoate (EB) to long-term castrated female rats.Cyclophenil has an activity 1/8110 times that of EB on uterine growth, and 1/1660 and 1/550 times that of EB in inhibiting LH and FSH. respectively. The hypophyseal 5\g=a\-reductase(expressed as DHT formation) was inhibited 1710 times less by cyclophenil than by EB. The other parameters considered were unsuitable to provide a statistically reliable estimate of the potency ratios between the two compounds. The data show that cyclophenil is an oestrogenic compound with peculiar characteristics. This substance is more effective in expressing its oestrogenic activity in central structures than in the peripheral ones.