Role of LH pulse amplitude and the rate of LH increase on oestradiol-17 beta secretion by immature rat ovaries in perfusion culture.
Immature rat ovaries were placed in perifusion culture and exposed to LH in a variety of patterns, while tonic levels of FSH (200 ng/ml) were maintained. Perifusate was collected every 5 min and assayed for oestradiol-17 beta. In Exp. I, LH was delivered at 50 ng/ml for 30 min then reduced to 0 ng/ml for an additional 30 min (50 ng/ml LH step) or as linear increasing concentrations reaching 50 ng/ml by 30 min of culture then linear decreasing concentrations reaching 0 ng/ml by 30 min of culture (50 ng/ml LH ramp). Although both delivery systems exposed the tissue to 250 ng LH over the 1-h culture period, only the 50 ng/ml step significantly increased oestradiol-17 beta secretion rates (P less than 0.05). In Exp. II, ovaries were not exposed to LH for the first 30 min of culture but then LH was administered at a concentration of 25 or 50 ng/ml for 30 min. The LH concentration was reduced to 0 ng/ml for an additional 30 min of culture. Oestradiol-17 beta secretion rates were increased 50% by both treatments. These results suggest that the mechanism by which an LH pulse stimulates the immature ovary to secrete oestradiol-17 beta is, in part (1) 'threshold'-dependent and not solely dependent on the amount of LH administered, and (2) dependent on the time required to achieve a 'threshold' level.
Peluso
J J
JJ
Department of Obstetrics and Gynecology, University of Connecticut Health Center, Farmington 06032.
Steger
R W
RW
D000818:Animals; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D007986:Luteinizing Hormone / Q000494:pharmacology*; D009924:Organ Culture Techniques; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013268:Stimulation, Chemical
D004958:Estradiol; D007986:Luteinizing Hormone