FOLLICLE-STIMULATING HORMONE BETA SUBUNIT MESSENGER RIBONUCLEIC ACID CONCENTRATIONS DURING THE RAT ESTROUS CYCLE

Serum follicle-stimulating hormone (FSH), pituitary FSH content and FSH beta subunit mRNA concentrations were measured at I to 3h intervals throughout the 4 day estrous cycle in rats. Serum FSH was stable (range 200-320 ng/ml) apart from the biphasic proestrus surge (5 fold elevation) which was present from l800h of proestrus through 0800 h on estrus. Basal FSH beta mRNA concentrations from late metestrus through the afternoon of proestrus were 0.10±0.04 f mol cDNA bound/100 ug pituitary DNA. The major increase in FSH beta mRNA began at 2000 h on proestrus, 2 h after the initial rise in serum FSH and peak mRNA concentrations (0.43±0.08 f mol cDNA bound) occurred at 0200 h on estrus. FSH beta subunit mRNA concentrations were again increased at 2300 h on estrus (peak 0.24 f mol cDNA bound) and remained elevated through 1700 h on metestrus. Pituitary FSH content was transiently increased during metestrus and diestrus, but was elevated at 1000 h through 1900 h on proestrus (peak 5-fold increase). FSH content ...