Ultrastructure of somatotroph cells at different times in a circadian period, in mice bearing a slow growing transplanted hepatoma.

An electronmicroscopic study of STH cells from mice bearing transplanted hepatomas was performed at different time points, in a circadian period. Normal mice served as controls. The STH cells of control animals showed circadian variations inplasmic reticulum and lysosomes, which suggest increased secretion of growth hormone along the light peroid. In mice bearing hepatomas the morphologic aspect of these organelles would also indicate an increase of STH elaboration at 1200 and 1600. These changes were more remarkable than in controls and mainly consisted of hypertrophy of the Golgi complex, extended and compact endoplasmic reticulum and presence of large amounts of lysosomes. Besides, another peak of secretion seems to be present at 0000, considering the dilatation of the Golgi complex and endoplasmic reticulum cisternae. Some findings are coincident with observations made by others in the hypophysis of animals bearing transplantable tumors, where circadian periodicity was not studied. The STH cytological circadian variations could be correlated with other variations could be correlated with other variables, such as STH values in plasma and hypophysis, and DNA synthesis and mitotic activity of SS1-H hepatoma.