Cytology of the pars anterior of the bovine adenohypophysis

Abstract

Abstract Selected samples from the pars anterior of 2 lactating cows, 2 normal calves, 3 thyroidectomized calves, and 12 heifers at different stages of the estrous cycle or in early pregnancy were examined by electron microscopy. Adjacent thick sections were differentially stained and routinely examined by light microscopy. Two acidophilic cell types were distinguished. One had granules with maximum diameters between 350 and 500 mμ. The other, containing granules with maximum diameters between 550 and 750 mμ, was frequently seen in lactating cows and midcycle or pregnant heifers. Basophilic cell types were not so clearly distinguishable. PAS‐positive, Alcian bluenegative basophils were most frequently seen in proestrous heifers, but basophils with Alcian blue, PAS‐positive granules were also present, and in some of these the granules were morphologically similar to those of the PAS‐positive cell type. Globular bodies, morphologically similar to those reported in amphibia but negative for acid phosphatase, were routinely observed in some of the Alcian blue, PAS‐positive basophils. The most significant change in estrous heifers and thyroidectomized calves was the development of large chromophobes with an extensive dilated rough endoplasmic reticulum. It was not possible clearly to relate these chromophobes individual basophilic cell types.