Ultrastructure of the cell types of the anterior hypophysis in a lizard. II. Somatotrophs and lactotrophs.

Somatotrophs of the teiid lizard Cnemidophorus lemniscatus are strictly localized in the rostral zone of the anterior hypophysis. Cells are prismatic and elongated, with basal nuclei. A dense hyaloplasm, a basal, serried system of stacked cisternae of rough endoplasmic reticulum, and predominantly spherical, medium-sized secretory granules that fill the supranuclear region characterize these cells. Secretory granules have moderate opacity, uniform dimensions, and a close bounding membrane. The well developed Golgi apparatus lies at one side of the nucleus. Regular variations correlative with environmental or experimental changes could not be verified in somatotrophs. Lactotrophs are mainly situated in the caudal and intermediate zones of pars distalis, reaching the rostral region when numerous and hypertrophic. They are avoid or pear-shaped, with a central nucleus. A basal system of stacked cisternae of rough endoplasmic reticulum, and the completely irregular shape of the secretory granules are typical of these cells. The granules, supranuclear and often large, have low density, a finely granular structure and a close bounding membrane. A fibrillar substance affords a mottled appearance to the hyaloplasm. The well developed Golgi apparatus is frequently found in the center of the basal region. The activity of lactotrophs, denoted by the size and number of cells, their spread in the gland, the amount of granules, and the development of the organelles, is much greater during the annual period of enhanced sexual function, and particularly in females.