RESUMO
The influence of 12-O-Tetradecanoylphorbol-13-acetate, an activator of proteinkinase C and A 23187, a calcium ionophore increasing cytosolic free calcium concentration on zinc metabolism was investigated in a study with 24 eight-week old rats. Twenty-four hours before killing, the rats (235 g body weight, 8 per group) were either injected intraperitoneally with TPA (1.6 x 10(-7) mol/kg body weight) or A 23187 (1.6 x 10(-6) mol/kg body weight). Control rats received the solvent dimethylsulfoxide. The application of TPA and A 23187 provoked a marked decline in feed intake accompanied by a reduction in body weight and liver mass. Serum concentrations of zinc were reduced significantly after A 23187 injections. TPA and A 23187 increased liver zinc levels by 20 and 30% respectively, if based on fresh and dry weight. The injections, however, did not alter total liver zinc. Liver metallothionein (MT) concentration was elevated 2.4-fold after TPA administration. The increase in response to A 23187 was only 1.5-fold and not significant. Mucosa MT levels were not altered. Serum activity of alkaline phosphatase was significantly reduced (TPA: -23%, A 23187: -31%). There was no change in serum glucose after injections. However, serum creatinine and urea were increased in response to A 23187. In conclusion, TPA and A 23187 had an effect on zinc metabolism of the rat, most marked in the case of MT induction in the liver. There is evidence that the reduced feed intake caused by TPA and A 23187 resulted in effects indistinguishable from those caused by fasting. Further experiments are needed to clarify whether proteinkinase C and cytosolic free calcium are directly involved in the regulation of zinc metabolism.
