Fine structure and pinocytic activity of the visceral epithelium of the rat yolk sac incubated in a culture medium with or without goat antirat-placenta-IgG.

The fine structure and pinocytic activity of the rat visceral yolk sac epithelium were examined electron microscopically after incubation in Krebs-Ringer-Phosphate solution containing either 125-I-labeled albumin or goat antirat-placenta-IgG or both compounds simultaneously. Addition of 125-I-albumin to the incubation medium stimulates the pinocytosis, whereas the addition of goat antirat-placenta-IgG, cross-reacting with the yolk sac tissue, causes a diminution of the pinocytic activity of the yolk sac epithelium. Fine structural alterations and lesions are generally noticed. Preincubation of yolk sacs in Krebs-Ringer-Phosphate solution containing goat antirat-placent-IgG and the subsequent postincubation in a new Krebs-Ringer-Phosphate medium with 125-I-albumin does not restore the original pinocytic activity of the visceral epithelial cells.