1968/04/01 by H. H. FEDER, Harvey H. Feder, J. A. RESKO +3 · 78 citations
Biochemistry, Genetics and Molecular Biology · Chemistry · Medicine · #Biology #Chemistry #Endocrinology #Estrogen and related hormone effects #Estrous cycle #Guinea pig #Hormonal and reproductive studies #Hormone #Hypothalamic control of reproductive hormones #Internal medicine #Luteal phase #Medicine #Ovulation #Receptivity
paper · doi:10.1677/joe.0.0400505
published in Journal of Endocrinology 40(4), 505-513 (Bioscientifica)
openalex publication_date 1968/04/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/11
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.