AJP - Endocrinology and Metabolism, Vol 243, Issue 5 380-E386, Copyright © 1982 by American Physiological Society
Effect of antimicrotubule agents on microtubules and steroidogenesis in luteal cells
S. Azhar and E. Reaven
This report represents an effort to reinvestigate the relationship of
steroid hormone processing with microtubule protein, using the highly
active progesterone-producing cells of superovulated immature rats as a
model steroid hormone system. For the most part, gonadotropin-primed rats
were used at 6 days and were reinjected with saline or various doses of
colchicine and vinblastine: after 3 h the animals were injected with human
chorionic gonadotropin (hCG, 10 IU) or saline for an additional hour.
Subsequently, the ovaries were perfused with fixative for morphological
studies or luteal cells were isolated for in vitro incubation with various
additives. The results are as follows: 1) luteal cell progesterone
synthesis is reduced in a dose- and time-dependent manner after treatment
with antimicrotubule drugs; 2) additional stimulating agents given in vitro
(hCG, Bt2cAMP, epinephrine) do not overcome the reduction produced by
treatment with antimicrotubule drugs; 3) luteal cells show normal protein
synthesis after treatment with antimicrotubule drugs; 4) luteal cells have
microtubules of unusual appearance that are insensitive to the action of
antimicrotubule agents. These results show that in the luteinized ovary,
both colchicine and vinblastine interfere with hormone-stimulated
steroidogenesis. Although the mechanism for the effect is not yet
understood, it does not appear to be related to the content of the intact
microtubules in luteal cells. Whether the drugs exert their action by
binding to the unassembled form of microtubule protein in the cells remains
to be determined.
