ATPase activities of inner and outer regions of the vitelline membrane during development

ATPase activity has been demonstrated to be present in the vitelline membrane complex of the hen's egg. This activity increases markedly after ovulation. The vitelline membrane complex has been isolated by dissection and studied in an Ussing chamber such that the inner and outer surfaces can be examined independently. Coupled activity has been detected whereby the presence of substrate on one side affects activity on the other side. Measurements demonstrate that the vitelline membranes of eggs laid in the fall have low enzymatic and no coupled activity. The vitelline membranes of eggs laid in the summer have high enzymatic and marked coupled activity. The coupled activity is reversed in the fertilized compared to the unfertilized egg. This study sheds light on both the physiological character of the ATPases and the roles played by the vitelline membrane in the development of the ovum prior to and after fertilization.