AJP - Endocrinology and Metabolism, Vol 246, Issue 3 243-E248, Copyright © 1984 by American Physiological Society
In vitro evidence of a role for inhibin in female rabbits
A. L. Goodman
To examine a regulatory role for inhibin in female rabbits, an in vitro
bioassay for inhibin activity was modified to use cultured rabbit pituitary
cells and charcoal-extracted porcine follicular fluid (pFFx) as a reference
preparation. pFFx inhibited follicle-stimulating hormone (FSH) release in a
dose-dependent manner in cultures from both intact (I) and castrate (C)
does at doses that also inhibited FSH release by cultured rat pituitary
cells. Basal FSH release by I cells was inhibited greater than 10% by 0.02%
(vol/vol) and greater than 90% by greater than or equal to 0.2% pFFx,
whereas in C cells maximal inhibition of FSH release plateaued at only
approximately 75%. FSH secretion was restored after removal of pFFx in day
2 media. Luteinizing hormone (LH) release by C cells was not inhibited at
any dose of pFFx, but in I cells LH was progressively inhibited to
approximately 60% of control levels during day 2 (but not day 1).
Charcoal-extracted media (0.25-1%) in which 5 X 10(5) rabbit granulosa
cells had been earlier cultured for 72 h produced a parallel inhibition of
FSH release. The present findings demonstrate that 1) rabbit pituitary
cells are responsive to inhibin, i.e., pFFx preferentially inhibited FSH
secretion in a direct, graded, and reversible manner and 2) rabbit
follicular granulosa cells secrete an inhibin-like substance.
