Effects of colchicine on the ovine corpus luteum: role of microtubules in the secretion of progesterone.

By 4 h after i.v. injection of ewes at the mid-luteal phase of the oestrous cycle with colchicine (1 mg/kg), the concentration of progesterone in peripheral plasma was halved while the content of progesterone in luteal tissue was doubled. The ultrastructure of the luteal tissue showed some specific drug-induced changes: microtubules were no longer present and the intracellular transport and secretion of granules associated with progesterone secretion appeared to be inhibited.