Cytochalasin B Inhibition of Luteinizing Hormone Action on Bovine Luteal Cells
The mechanism of action of luteinizing hormone (LH)1 in stimulating steroidogenesis in the corpus luteum has been studied for some time, and a concept of some of the major aspects of this mechanism has emerged (1). LH binds to receptors on the luteal cell surface and this binding brings about an activation of adenylate cyclase and an increase in the concentration of cyclic AMP. This cyclic AMP in turn binds to the regulatory subunit of a cyclic AMP-dependent protein kinase causing the release and activation of the catalytic subunit. The increase in protein kinase is believed to mediate most if not all of the effects of LH on the steroidogenic pathway, but its precise mechanism is not known at this time. The limiting step in the steroidogenic pathway appears to be between cholesterol and pregnenolone but there are several ways in which this step might be accelerated (1). One possibility is that LH and cyclic AMP might promote the transport of cholesterol into mitochondria, and there is some experimental support for this from studies on the mechanism of action of ACTH in stimulating adrenal corticosteroidogenesis (2,3). Furthermore, microfilaments, a contractile element of the cells, have been implicated in the ACTH stimulated transport of cholesterol into the mitochondria of Y-1 mouse adrenal tumor cells (4). We have attempted to investigate the possible role of microfilaments in the mechanism of action of LH in the luteal cell. Our approach has been to study the effect of an inhibitor of microfilament function, namely cytochalasin B.
KeywordsLuteinizing Hormone Corpus Luteum Paired Comparison Luteal Cell Progesterone Synthesis
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