Abstract
Immature female rats were injected with a single dose (10 IU) of pregnant mare serum gonadotropin to induce growth and maturation of ovarian follicles. Using such ovaries as a model, we tested the effects of low molecular weight subfractions of charcoal-adsorbed bovine follicular fluid (FF-c) on (a) radioiodinated human FSH ( 125I-hFSH) binding to ovarian homogenates, (b) ovine FSH-stimulated adenylate cyclase activity in granulosa cell homogenates and (c) cAMP production by intact granulosa cells. The follicular fluid was fractionated by ultrafiltration through membranes of differing pore-sizes into low molecular weight components of 1000–5000 (passing Amicon HIP-5 hollow fibers but retained by Amicon UM-2 membrane) and 500–1000 (passing Amicon UM-2 membrane but retained by Amicon UM-05 membrane). These low molecular weight fractions inhibited 125I-hFSH binding to ovarian receptors, FSH-stimulated cAMP production by rat granulosa cells and FSH-stimulated, as well as fluoride-ion-stimulated adenylate cyclase activity in granulosa cell homogenates. Inhibition of FSH-stimulated adenylate cyclase activity by the FF subfractions was non-competitive as determined by double reciprocal plot analysis. Our results suggest that modulation of FSH effects on granulosa cells may be mediated by low molecular weight constituents of follicular fluid.
Published Version
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