[Effects of clenbuterol on nitrogen metabolism and G6PDH activity of rat hepatocyte].

AIM: To study the effects of beta 2-adrenergic receptor-selective agonist clenbuterol on nitrogen metabolism and glucose-6-phosphate dehydrogenase activity of rat hepatocyte and its pharmacological mechanism.

METHODS

Biochemical methods were used to study the influence of clenbuterol on urea-nitrogen concentration of hepatocyte culture medium, 3H-leucine incorporation into hepatocyte, insulin-like growth factor I (IGF-I) production and glucose-6-phosphate dehydrogenase (G6PDH) activity of rat hepatocyte.

RESULTS

The results showed that urea-nitrogen production by cultured rat hepatocytes was markedly affected with clenbuterol treatment (1 x 10(-6) mol.L-1), urea-nitrogen concentration of culture medium was decreased by 25.51% (P < 0.05) compared with control. The inhibitory effect of hepatocyte urea-nitrogen production of clenbuterol was blocked by propranolol, a beta-adrenoreceptor antagonist (1 x 10(-6) mol.L-1), but hepatocyte urea-nitrogen level was not affected with propranolol treatment only (P > 0.05). The content of 3H-leucine incorporation in rat hepatocyte was significantly increased by 23.35% (P < 0.05) with clenbuterol-treatment (1 x 10(-6) mol.L-1), and the enhanced effect of 3H-leucine incorporation into hepatocyte was antagonized by propranolol (1 x 10(-6) mol.L-1. The level of 3H-leucine incorporation of rat hepatocyte was not influenced by propranolol alone. IGF-I production of rat hepatocyte might be affected by clenbuterol. IGF-I concentration of culture medium was increased by 39.46% with clenbuterol (1 x 10(-6) mol.L-1), but no significant difference was found compared with the control (P > 0.05). Moreover, G6PDH activity of rat hepatocyte was significantly decreased by 43.36% (P < 0.05) with clenbuterol treatment (1 x 10(-6) mol.L-1), and the declined effect of clenbuterol was antagonized by propranolol. G6PDH activity of rat hepatocyte was not affected on condition that propranolol was administered alone (P > 0.05).

CONCLUSION

It is suggested that clenbuterol may regulate nitrogen and fat metabolism by means of increasing nitrogen retention and protein synthesis, and decreasing G6PDH activity of rat hepatocyte for pharmacological effects.