Effects of cyproheptadine on the rat yolk sac membrane and embryonic development in vitro

Abstract

1. Electron-microscopic examinations of rat embryonic yolk sacs treated in vitro with 1˙5 × 10⁻⁵ M cyproheptadine showed proliferation of the lysosomal structures; other organelles remained unaffected, and also overall yolk-sac growth and vascularization were comparable to non-treated samples.

2. Radioactive measurements with ¹²⁵I-labelled albumin showed that yolk sacs and embryos of the cyproheptadine-treated group incorporated less radioactivity than the controls.

3. Embryos inside the yolk sacs, treated either for 24 or 48 h, were severely retarded in growth and differentiation (∼ 50% of the controls).

4. It is suggested that the specific action of cyproheptadine on yolk-sac lysosomal structures, combined with reduced macromolecular transport, is the cause of inhibited embryonic development.