Ultrastructural localization of acid phosphatase in thyrocytes of rats with thyroid hyperfunction

Abstract

Acid phosphatase was detected electron-cytochemically in lysosomes which appeared in large numbers in the follicular cells of the hyperplastic rat thyroid gland. The remaining types of granules (mature secretory granules, lipid granules), the number of which also increased appreciably during functional stress on the thyrocytes, did not contain the reaction product. By the character of distribution of acid phosphatase the lysosomes could be subdivided into three main groups: those with a dense homogeneous residue and those with residue in the form of densely or infrequently distributed circular grains. The heterogeneity of the lysosomes may be attributed to differences in their functional state. Besides in the lysosomes, the reaction product was found in pale cells as a sprinkling of widely scattered dark grains. These drops evidently appeared as the result of fusion of droplets of colloid with lysosomes. The acid phosphatase of the lysosomes in this case participates in hydrolysis of the secretion product of the cells with the formation of the active substances.