Abstract
The temporal relationship between the levels of LH in peripheral plasma and in follicular fluid of ovarian follicles in anaesthetized sheep were investigated for a 10-h period after a single i.m. injection of LH releasing hormone (LH-RH; 100 microgram). The ovarian secretion rates of oestradiol and androstenedione and the levels of these steroids accumulating in different sized follicles at varying time-intervals after the LH-RH injection were also compared. The data show that the rates at which pituitary LH enters and leaves the intrafollicular fluid-filled spaces are substantially slower than those of peripheral blood. Two hours after LH-RH injection the levels of LH in plasma had increased from 1 to 200 ng/ml, whereas in the follicle the levels remained at approximately 2ng/ml. Ten hours after the LH-RH injection, the levels of LH in plasma had returned to basal values (approximately 1.4 ng/ml) but in both small and large follicles the levels of LH (approximately 20 ng/ml) were comparable to those present in similar sized follicles 4h earlier. The data also indicate that more than 90% of the oestradiol produced by a large antral follicle (greater than or equal to 5 mm diameter) probably enters the bloodstream without first accumulating within the follicular antrum. Finally it is concluded that the clearance of the small amount of oestradiol which does accumulate in the follicular antrum is negligible compared with the clearance of this hormone from peripheral plasma.
Published Version
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