OXYTOCIN SYNTHESIS AND SECRETION FROM BOVINE CORPORA-LUTEA EXPOSED IN-VITRO TO CYCLOHEXIMIDE AND COLCHICINE

Two experiments were conducted to study the effects of cycloheximide a nd colchicine on prostaglandin F-2 alpha (PGF(2 alpha))-induced secret ion and synthesis of oxytocin in bovine luteal tissue in vitro. Corpor a lutea were collected from beef heifers on Day 8 of the estrous cycle . In Experiment 1, incorporation of[C-14]-leucine into oxytocin synthe sized and secreted by luteal slices after exposure to PGF(2 alpha), cy cloheximide and cycloheximide plus PGF(2 alpha) was examined. In Exper iment 2, synthesis and secretion of oxytocin were evaluated in luteal slices incubated with colchicine and PGF(2 alpha) alone and in combina tion. Cycloheximide inhibited incorporation of labeled leucine into lu teal proteins by more than 90% and no labeled oxytocin was detected in the media or tissue. Prostaglandin F-2 alpha induced significant secr etion of oxytocin that was not inhibited by cycloheximide. Tissue leve ls of oxytocin after incubation with cycloheximide and/or PGF(2 alpha) did not differ and were similar to those of the incubated control. Co lchicine alone did not suppress oxytocin secretion and did not alter t he ability of PGF(2 alpha) to induce significant secretion of this non apeptide. Tissue concentrations of oxytocin after incubation with colc hicine and/or PGF(2 alpha) did not differ. These studies indicate that secretion and replenishment of luteal oxytocin in vitro is not contin gent upon de novo protein synthesis. Inability of colchicine to suppre ss oxytocin secretion and synthesis may have been due to the short dur ation of exposure of luteal tissue to the drug.