Effect of porcine follicular fluid injection on FSH secretion in the immature female rat

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Abstract
Porcine ovarian follicular fluid (pFF) contains a substance capable of selectively suppressing FSH secretion in adult rats. The effectiveness of this material in prepubertal female rats was examined. Steroids were removed from pFF or pig serum by adsorption to charcoal. Twenty-four hours after sham or bilateral ovariectomy, at 17 days of age, the rats received an intraperitoneal injection of 0.4 ml charcoal-extracted pFF or serum. Eight hours after injection animals were killed by cervical dislocation and blood collected. Serum estrogen and FSH concentrations were estimated by radioimmunoassay. Ovariectomy reduced total serum estradiol from 181 ± 25 to 77 ± 18 pg/ml (mean ± SEM) and pFF had no effect on this response. Ovariectomy caused an increase of serum FSH from 1275 ± 239 to 2392 ± 122 ng FSH (RP – 1)/ml in control and gonadectomized rats, respectively. Post-ovariectomy hypersecretion of FSH was completely Mocked when animals were treated with pFF. in sham-ovariectomized animais pFF was unable to suppress FSH secretion. These results support the notion that the relatively high levels of FSH found in intact female rats of this age might be explained in part by a low responsiveness to the inhibin-like component of follicular fluid.