Effects of EGF on the mass of inositol 1,4,5-trisphosphate and SN(1,2)-diacylglycerol in freshly isolated rat hepatocytes: comparison with vasopressin.
We measured the masses of inositol 1,4,5 trisphosphate (Ins(1,4,5)P3) and diacylglycerol (DAG) in hepatocytes in response to both epidermal growth factor (EGF) and vasopressin. EGF at 25 nM did not alter Ins(1,4,5)P3 content of hepatocytes. However, the combination of 100 nM EGF concentration and incubation with lithium did increase Ins(1,4,5)P3 content. This increase was only one tenth of that elicited by vasopressin in parallel incubations. This finding resolves a controversy concerning the ability of EGF to increase Ins(1,4,5)P3 in hepatocytes, and argues against a role for phosphoinositide hydrolysis in EGF action in hepatocytes. Both EGF and vasopressin caused a rapid (30 s) increase in DAG content. A delayed increase in DAG content, that was maximal after several minutes, was observed only for vasopressin. The rapid increase in DAG content implies an activation of protein kinase C for both EGF and vasopressin.
Cerpovicz
P F
PF
Department of Biochemistry, Kansas State University, Manhattan 66506.
Ochs
R S
RS
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D004075:Diglycerides / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D014667:Vasopressins / Q000494:pharmacology*
C011439:1,2-diacylglycerol; D002712:Chlorides; D004075:Diglycerides; D014667:Vasopressins; D004533:Egtazic Acid; D004815:Epidermal Growth Factor; D015544:Inositol 1,4,5-Trisphosphate; D008094:Lithium; D011493:Protein Kinase C; D018021:Lithium Chloride; D002118:Calcium