Glucagon, vasopressin and angiotensin all elicit a rapid, transient increase in hepatocyte protein kinase C activity.
Challenge of intact hepatocytes with one of the hormones vasopressin, angiotensin and glucagon or with the phorbol ester phorbol 12-myristate 13-acetate (PMA) led to a rapid increase in the activity of protein kinase C found in both cytosol and membrane fractions. Maximal activation by hormones occurred within 1-6 min of challenge of cells, after which activity declined. In membrane fractions protein kinase C activity return to basal levels some 15 min after exposure of cells to either angiotensin or glucagon. In cytosol fractions of cells challenged with hormones a second phase of activation ensued after about 10 min, with levels of protein kinase C activity remaining elevated above basal level 15 min afterwards. Activity changes elicited by PMA were rather different; it took about 15 min to achieve maximal activation of cytosolic protein kinase C activity. In membranes of cells challenged with PMA, an initial rapid and transient activation was followed by a sustained increase in activity occurring about 10 min after exposure of cells to this ligand. Only when hepatocytes were challenged with PMA was the translocation of protein kinase C from the cytosol to membrane fraction observed. The kinetics of PMA-induced translocation suggested that it accounted for the second phase of the increase in membrane protein kinase C activity which was unique to this ligand.
Tang
E K
EK
Department of Biochemistry, University of Glasgow, Scotland, U.K.
Houslay
M D
MD
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D005934:Glucagon / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D011493:Protein Kinase C / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology*
D014667:Vasopressins; D000804:Angiotensin II; D015124:8-Bromo Cyclic Adenosine Monophosphate; D005934:Glucagon; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate