Ultrastructural localization of phosphatases in the rat parathyroid gland

Ultrastructural localizations of phosphatases were observed in the rat parathyroid gland. Activities of alkaline phosphatase and adenosine triphosphatase were found on the caveolae or pinocytotic vesicles of the capillary endothelia. In the parenchymal cells, they were demonstrated to be stronger both at the plasma membranes facing the pericapillary space and at their transitional portions to the lateral plasma membranes than at the remaining lateral plasma membranes including microvilli. Activities of thiamine pyrophosphatase and inosine diphosphatase were detected on one or two layers of lamellae at the inner face of the Golgi apparatus, and the localization of the latter enzyme was more restricted than that of the former. Additionally, they were sometimes observed also on the blood capillary wall. Contrasted to these enzymes, acid phosphatase activity was demonstrated on the entire Golgi lamellae besides lysosomes, but not on multivesicular bodies, vacuolar bodies and storage granules.