AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 2 184-R189, Copyright © 1984 by American Physiological Society
Regulation of ovarian follicular growth and steroidogenesis by low-amplitude LH pulses
J. J. Peluso, M. L. Gruenberg and R. W. Steger
A perifusion culture system controls the delivery of regulatory agents such
that their concentration in the culture chamber is known at each and every
point in time. The concentration in the culture chamber is predicted by the
following equation: C(t) = Cf + (Ci - Cf)e(-R.t)/V, where C(t) is
concentration in culture chamber (CC) at time t, Cf is concentration in
holding flask (HF) (final CC concentration at t = infinity), Ci is initial
CC concentration (t = 0), R is rate of media delivery from HF to CC (ml/h),
V is volume of medium in CC (ml), and t is time (h). With this perifusion
culture system, metestrous rat ovaries were exposed to tonic levels of
follicle-stimulating hormone (FSH) and either tonic levels or hourly pulses
of luteinizing hormone (LH). Both groups, however, received the same amount
of FSH and LH. Compared with tonic levels, hourly pulses of LH increased
estradiol-17 beta and suppressed testosterone secretion. In addition,
pulsatile LH caused 1) a reduction in the atresia of small and midsized
antral follicles, 2) an increase in atretic large follicles, and 3) an
increase in the percent of growing midsized follicles. These results
clearly demonstrate that ovarian responses depend on the pattern of LH
stimulation. Since the LH pulses used in this study mimic in vivo
metestrous levels, the LH pulses may be important in controlling ovarian
function in vivo. The mechanism by which the ovary can distinguish between
tonic and pulsatile stimuli remains to be determined.
