Inhibition of Ovulation in Hamsters by the Protein Synthesis Inhibitors Diphtheria Toxin and Cycloheximide

Abstract

Summary

Diphtheria toxin and cyclohex-imide, structurally unrelated translational inhibitors of protein synthesis, inhibited ovu-lation in hamsters. Inhibition resulted from i.p. injection given well after the 2:30 pm release of pituitary luteinizing hormone (LH) that initiates the 11-hr ovulatory process. Thus it may be concluded that these agents inhibit ovulation by direct action on the ovaries. Both luteinization and follicular rupture were inhibited. Follicles inhibited by cyclo-heximide were similar histologically to control follicles prevented from ovulating by central blockade of LH release with phenobar-bital, whereas follicles inhibited by toxin contained shrunken oocytes and necrotic granu-losa cells. Low doses of both agents inhibited ovulation only when injected within 5 hr after LH release. However, high doses were effective at later times. Similar ovulation inhibition responses to both the microbial toxin and cycloheximide at high doses suggest that protein synthesis essential for ovulation occurs throughout the 11-hr ovulatory process initiated by LH and is not restricted to the early part of this period.

We thank Dr. Louis Kasza (Food and Drug Administration) for histological analysis of the sectioned ovaries.