Effects of ovariectomy and hypervitaminosis A on lysosomes of the rat conceptus

This report is concerned with some biochemical effects of ovariectomy and hypervitaminosis A on cell organelles, with particular emphasis on the lysosomes, of embryos, yolk sacs, and placental labyrinths of 13‐day pregnant rats. The two parameters considered were lysosomal stability and the distribution of enzymes in fractions obtained by differential centrifugation. Lysosomal stability was determined by measuring (1) the amount of “free” enzyme activity, i.e., the amount of enzyme in the cytoplasmic extracts of the three tissues measured in the presence of isotonic sucrose and (2) the amount of “nonsedimentable” enzyme. Excess vitamin A produced no change in the latency of acid phosphatase or β‐glucuronidase in any of the tissues when compared with controls. Following ovariectomy there was marked labilization of both enzymes in embryos, increased labilization of β‐glucuronidase in placentas, and little change in yolk sacs. The distributions of the lysosomal enzymes in control fractions were not the same in the three tissues, indicating differences in size, shape, and/or density of the lysosomes. There was no change in the distribution of reference enzymes after hypervitaminosis A. Ovariectomy produced increased solubilization of β‐glucuronidase in the three tissues and a lesser increase in soluble acid phosphatase in embryos, indicating lack of uniformity in the lysosomes.