CHANGES IN FOLLICULAR-FLUID AND SERUM CONCENTRATIONS OF STEROIDS IN PMS TREATED IMMATURE RATS FOLLOWING LH ADMINISTRATION

The effect of an ovulatory dose (10 μg/rat) of luteinizing hormone (NIH-LH-B8) on follicular fluid (FF) and peripheral serum concentrations of steroids in pregnant mare's serum (PMS) treated rats (4 IU/rat) was studied over a 10 h period. Within 1 h of LH administration, FF and serum concentrations of progesterone (P) had risen 7- and 10-fold, respectively, the concentrations remaining elevated for the remainder of the experiment. In contrast, the FF and serum concentrations of androgen (A) and estradiol-17β (E) after rising only slightly over the first 1-2 h after LH administration, steadily declined thereafter to reach extremely low levels by 10 h. These findings not only show the range in concentrations of rat FF steroids but also demonstrate that approaching ovulation in the rat is associated with a change in follicular steroidogenesis with P production being stimulated while A and E production is suppressed. In addition, these findings indicate that the measurement of FF steroids is a useful means of assessing the steroidogenic activity of the follicle.