Bovine luteal cyclic AMP and cyclic GMP phosphodiesterase activity; sensitivity to various drugs and hormones

Abstract

Previous studies have shown the presence of two forms of cyclic AMP phosphodiesterase activity in bovine corpus luteum tissue [l] . These enzymes have K, values of approx. 2 X 1 O4 M and 1 X 1 Oe6 M, similar to those of other tissues studied [2]. However to our knowledge the presence of cyclic GMP phosphodiesterase activity has not been demonstrated in ovarian tissue. This study indicates that a cyclic GMP phosphodiesterase is present in bovine luteal tissue. The effects of known inhibitors of phosphodiesterase activity were studied to establish whether they had selective effects in inhibiting either the cyclic AMP or cyclic GMP phosphodiesterase from ovarian tissue. It has been previously reported that many inhibitors of phosphodiesterase are more effective in preventing cleavage of cyclic AMP than cyclic GMP [2] , although this varies from tissue to tissue [3] . The effects of various drugs and hormones were determined with a view to finding doses at which different effects might be dissociated. Of special interest were the effect of indomethacin, which is a potent inhibitor of prostaglandin biosynthesis [4] and flufenamic acid which antagonises the effect of prostaglandin Fza [S] since these compounds have been reported to also have the ability to inhibit phosphodiesterase activity in other tissues [6,7].