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Search for other papers by D. A. GOLDFOOT in
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Search for other papers by J. A. RESKO in
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SUMMARY
Male guinea-pigs born to females injected with cyproterone acetate (CA) from day 28 to 58 of gestation developed non-tubular hypospadiac penes and stunted seminal vesicles and prostate glands. When adult animals were stimulated with exogenous or endogenous androgens, secretory failure and only minimal growth was observed in the accessory organs. The concentrations of endogenous testosterone in systemic plasma from intact CA males were not different from those in control males, but the uptake and distribution of [1,2-3H]testosterone in castrated CA males did not conform to control values. Deficiences in mounting, intromission and ejaculatory patterns were observed in CA males compared with controls. Lordosis, the primary behavioural response used as a criterion of 'feminization', was never observed in CA males even when large concentrations of oestrogens were administered. The results suggest that target organ insensitivity to testosterone in adulthood can be the result of deficient androgenic stimulation during embryological differentiation.
Search for other papers by D. S. DHINDSA in
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Search for other papers by J. METCALFE in
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SUMMARY
The effect of various routes of administration on the plasma concentrations of progesterone was studied in Pygmy goats. Oral administration, even in extremely high doses, gave low plasma concentrations which returned to normal within 24 h. Progesterone given by subcutaneous or intra-abdominal implantation in silicone rubber (Silastic) envelopes caused a marked rise in the plasma concentration of progesterone, values reaching 10–30 ng/ml at 10–20 days but then declining. A fall in plasma concentration despite continued administration was also observed with daily intramuscular injections of large doses of progesterone. This observation suggests that some physiological mechanism prevents sustained high plasma levels of this hormone.
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Search for other papers by H. H. FEDER in
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SUMMARY
Testosterone and androstenedione levels in plasma and testicular tissue of developing rats were measured using gas—liquid chromatography with electron capture detection. The major androgen of both the adult and early postnatal period of development was testosterone. Pooled plasma from 230 one-day-old male rats contained 0·027 μg. testosterone/100 ml. The concentration of testosterone in the testes at this age was 0·328 μg./g. wet tissue. With increasing age there was a decline in testosterone concentration in plasma as well as in gonadal tissue which lasted until about the age of 30 days. The period from 40 to 60 days was characterized by an increasing concentration of testosterone in the plasma and gonads. During adulthood, testosterone reached concentrations as high as 0·202 μg./100 ml. peripheral plasma.
Androstenedione could not be detected in the circulation during the critical period of neonatal neural sexual differentiation, but it was present in the testes at this stage. In the pubertal and adult stages androstenedione was found in the plasma and testes. Its concentration, particularly in adulthood, was not as great as that of testosterone.
These results indicate that testosterone is present in plasma and testicular tissue of the rat during the neonatal period when behavioural and physiological sexual differentiation is presumed to occur.
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SUMMARY
The quantities of circulating progesterone and its 20-dihydro metabolites in cyclic female guinea-pigs were estimated by gas chromatography with electron capture detection. Forty-four animals were divided into 13 groups of approximately equal size according to stage of the oestrous cycle. The day on which a lordosis response could be elicited was designated Day 0 of the cycle. In the first few hours of sexual receptivity on Day 0 progesterone levels were 0·36 ± 0·07 μg./100 ml. arterial plasma. The ovaries were pre-ovulatory at this stage. After 5 to 12 hr. of behavioural receptivity progesterone levels dropped to 0·04 ± 0·01 μg./100 ml. plasma, and at the termination of receptivity (just after ovulation) progesterone was almost completely undetectable.
The concentration of progesterone increased gradually after ovulation reaching a peak about Day 9 (0·30 ± 0·05 μg./100 ml. plasma) and then fell to undetectable levels by Day 15. The 20-dihydro metabolites of progesterone were not present in significant quantities at any stage of the cycle.
It is concluded that in guinea-pigs a surge of progesterone occurs approximately 8 to 12 hr. before ovulation and coincides with the onset of oestrous behaviour. The plasma concentration of progesterone at this pre-ovulatory stage is at least as high as that measured at any point during the luteal phase.
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Search for other papers by J. A. RESKO in
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Search for other papers by R. W. GOY in
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SUMMARY
The concentrations of progesterone and 20α-hydroxypregn-4-en-3-one in the systemic circulation of 5-day cyclic rats were estimated by gas—liquid chromatography with electron capture detection. Behavioural receptivity (lordosis) was the criterion taken to mark the start of the oestrous cycle. Progesterone levels were highest during the pre-ovulatory period when lordosis was being displayed (3·11 ± 0·41 μg./100 ml. plasma). Several hours later, at the end of the receptive period, the progesterone concentration had declined to 1·18 ± 0·24 μg./100 ml. plasma. Except for a small mid-cycle increase the concentrations throughout the remainder of the oestrous cycle remained below this level until the morning of expected behavioural receptivity, when they rose to 2·14 ± 1·15 μg./100 ml. plasma. The concentration of 20α-hydroxypregn-4-en-3-one did not vary significantly with the cycle.
After ovariectomy, the 20α-dihydro metabolite disappeared from the circulation within 48 hr. Progesterone, however, was measurable in the plasma even 25 days after ovariectomy. After ovariectomy and adrenalectomy, progesterone was undetectable within 8 hr. It was concluded that under anaesthesia and surgical stress the rat adrenal may release significant amounts of progesterone.
