Effects of oestradiol-17β and LRH upon the two fractions of pituitary follicle-stimulating hormone separated by concanavalin-A chromatography

Abstract

The effects of oestradiol-17 beta (E2) and LRH upon the two fractions of pituitary follicle stimulating hormone (FSH) obtained by concanavalin A (Con A) chromatography were studied. Anterior pituitary glands were removed from adult intact rats at different times throughout the oestrous cycle, and from long-term ovariectomized (Ovx) rats after specific endocrine treatments. The presence, relative ratio and biological activity of each Con A separable FSH fraction were assessed by a specific radioimmunoassay and by an in vitro bioassay. After separation by concanavalin A chromatography, glands from intact rats sacrificed during the days of oestrus, dioestrus 1 and dioestrus 2, exhibited constant relative ratios (U:B FSH ratio) of the two FSH fractions so separated (Con A unbound and bound FSH), whereas donors sacrificed at the morning and early afternoon (13.00-15.00 h) of the day of pro-oestrus, showed the highest U:B FSH ratio; this ratio abruptly declined at the time of the FSH surge, after 15.00 h of pro-oestrus. Ovx rats exhibited lower ratios than intact animals. Pituitary extracts from Ovx donors under short-term (20 h) E2 exposure (condition which decreased pituitary sensitivity to LRH), showed the lowest U:B FSH ratio, whereas glands from Ovx rats exposed to conditions which caused increased pituitary LRH exposure (immediately before the oestradiol-induced FSH surge or after injection of 100 ng of LRH) showed an increase in their U:B FSH ratio, as compared with Ovx and Ovx + E2 (20 h) rats.(ABSTRACT TRUNCATED AT 250 WORDS)