The effects of various treatments in vivo on the intracellular contents of the Golgi apparatus and microsomes (endoplasmic reticulum) in rat liver were studied. Partial hepatectomy increased the content of Golgi apparatus. Laparotmy also increased the content of Golgi apparatus, but to a lesser extent than partial hepatectomy. In contrast, the content of microsomes remained unchanged by these treatments. On the other hand, the plasma seromucoid content was markedly increased by laparotomy, but unchanged by partial hepatectomy. Papain administration also caused an increase in the content of Golgi apparatus. The contents of both organelles were increased by the injection of phenobarbital. These results indicate that the control mechanisms of proliferation of Golgi apparatus are different from those of endoplasmic reticulum. These findings are discussed in relation to the functions of the Golgi apparatus, and it is suggested that  the major function of the organelle at a given time is determined by the major metabolic demands at that time.
Animals Galactosyltransferases