Evidence that dl-propranolol increases thymidine kinase activity, cell mitosis, and β-adrenoceptors during rat liver regeneration

Background. Adrenoceptor stimulation has been described as an important factor in liver regeneration. We examined the effects of the β-adrenoceptor antagonist, dl-propranolol, during early steps of regeneration after partial hepatectomy in rat. s. Thymidine kinase (TK) activity, cell mitosis, and β-adrenoceptors were measured after a single intraperitoneal (i.p.) injection of dl-propranolol (10 mg/kg) immediately following 70% partial hepatectomy. Enzyme activity was measured as [3H] thymidine (dThd) monophosphate; mitotic index was determined after tissue staining, and β-adrenoceptors were quantified by saturation binding of [3H] dihydroalprenolol. Liver regeneration was followed for 3 days. s. dl-Propranolol increased TK activity as early as 12 h postsurgery, after which it leveled off at 24 h and declined at later times; mitotic index increased from 12 to 48 h after injection and β-adrenoceptors augmented at 24 h compared to partial hepatectomy alone. sions. dl-Propranolol up-regulated β-adrenoceptors early after partial hepatectomy with an increase in TK activity and augmented hepatocyte mitosis. These data may suggest that dl-propranolol modulates, probably via β-adrenoceptor blockade, early steps of liver regeneration.