Abstract
The electron microscopic appearance of normal hamster liver is illustrated, and attention is drawn to certain unusual features of hepatocyte fine structure that have not hitherto been described. Examination of liver cells from animals receiving repeated intraperitoneal injections of phenobarbital, reveals a spectacular hypertrophy of the agranular reticulum and a depletion of particulate glycogen. The increase in smooth endoplasmic reticulum cannot be explained by loss of ribosomes from the granular reticulum and is regarded as an absolute gain of new membrane. Numerous examples of continuity between granular and agranular reticulum are observed, and it is suggested that protein synthesis associated with the granular reticulum contributes to the formation of the new smooth-surfaced membranes. In discussing the morphological alterations of the liver induced by phenobarbital, numerous biochemical changes reported in the literature have been reviewed in an effort to gain a clearer view of the over-all significance of the agranular reticulum in liver cell function. The evidence points to an important role in hydroxylation and elimination of lipid-soluble drugs, and in cholesterol and steroid hormone metabolism. There are indications that it also plays some role in carbohydrate metabolism, but the exact nature of its participation cannot yet be defined.