AJP - Endocrinology and Metabolism, Vol 244, Issue 5 435-E441, Copyright © 1983 by American Physiological Society
Porcine granulosa cell desensitization: prolonged FSH-responsive cAMP production in vitro
A. R. LaBarbera and A. E. Fisher
Granulosa cells from small (1-2 mm) follicles of porcine ovaries produced
cAMP in response to follicle-stimulating hormone (FSH); they produced
little cAMP in response to human chorionic gonadotropin (hCG) or to cholera
toxin. Production, estimated by quantification of total cAMP (medium +
cells) by radioimmunoassay, appeared to be episodic in the absence or
presence of the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine
(MIX) and continued for at least 20 h. Results of dual incubation
experiments with thorough washing of cells between incubations indicated
that cells remained responsive to FSH, to hCG, and to cholera toxin after
prior exposure to homologous stimulator. Preincubation of cells for 3 h in
the absence of stimulator enhanced FSH responsiveness. In experiments with
heterologous stimulators in two incubations, first, preincubation with FSH
enhanced subsequent hCG and cholera toxin responsiveness; and second,
preincubation with hCG or cholera toxin did not affect FSH responsiveness.
Desensitization of FSH-activated adenylate cyclase was never greater than
35%; the degree of attenuation was dependent on FSH concentration and
duration of exposure to FSH. Cells perifused with medium containing MIX and
a maximally effective concentration of FSH for 5 h released cAMP
continuously. In summary, the results indicated that porcine granulosa
cells do not become unresponsive to FSH after prolonged exposure to FSH in
vitro.
