Abstract
Ca2+-ATPase in the tanycyte ependyma of the third ventricle was investigated in rats using a cytochemical method. Reaction products were detected in the plasma membrane of the tanycytic ependymal lining of the third ventricle and were especially marked at the apical microvilli of its more dorsal part adjacent to the ventromedial nucleus. The positive reaction was dependent on calcium. A difference between the apical and the lateral plasma membrane was observed with respect to substrate specificity. The substitution of ADP for ATP caused no reaction product in the former, while exhibiting activity in the latter. The property of the enzyme seems to be different between the two. Ca2+-ATPase in tanycytes may have a role in the active transport of substances and in the regulation of intraventricular and intracellular Ca2+ concentrations.
