A method for studying rat embryonic metabolism by microcannulation of the vitelline circulation

A novel technique which involves the cannulation of the vitelline vessels of the 11.5 days rat embryo is described; this has allowed the introduction of both macromolecular and particulate substances directly into the embryo, thus bypassing the digestive and metabolic activity of the visceral yolk sac and facilitating the study of the fate of such substances within the embryo. The method does not affect the growth of the conceptus in vitro providing that inert solutions (e.g. azo blue dye in Hank's balanced salt solution) in volumes of less than 1.0 microliter are employed. When India ink is injected, the vitelline vessels and the intraembryonic vessels are seen to be extensively perfused. Approximately 80% of injected 125I-labelled polyvinylpyrrolidone is retained by the conceptus after injection, and it is distributed mainly in the embryo and exocoelomic cavity.