Comparative hydrolase cytochemistry of the mature guinea-pig and marmoset yolk sac with special reference to proteases.

Proteases and gamma-glutamyl transferase linked to plasma membranes, lysosomes and secretion granules were investigated cytochemically together with phosphatases, glycosidases and non-specific esterases in the mature guinea-pig and marmoset yolk sac. Species-independently, the yolk sac epithelial cells showed high activities of lysosomal proteases, glycosidases and non-specific esterases and phosphatases, whereas species-dependent patterns were found for plasma membrane proteases, gamma-glutamyl transferase and phosphatases. Furthermore, the guinea-pig yolk sac epithelium showed marked regional differences and that of both species intercellular differences, which allowed the subdivision of yolk sac epithelial cells in various types. The high activities of all lysosomal enzymes suggests their general importance for the yolk sac function in guinea-pigs and marmosets. The different equipment of the plasma membrane with proteases, gamma-glutamyl transferase and phosphatases indicates a more species-specific physiological role of this part of the yolk sac epithelial cells.