AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 5 1232-R1240, Copyright © 1989 by American Physiological Society
Protein phosphorylation in isolated hepatocytes of septic and endotoxemic rats
I. V. Deaciuc and J. A. Spitzer
Department of Physiology, Louisiana State University Medical Center, New Orleans 70112.
The purpose of this study was to investigate possible alterations induced
by sepsis and endotoxicosis in the late phase of Ca2+-dependent signaling
in rat liver. Hepatocytes isolated from septic or chronically endotoxin
(ET)-treated rats were labeled with [32P]H3PO4 and stimulated with various
agents. Proteins were resolved by one-dimensional polyacrylamide gel
electrophoresis and autoradiographed. Vasopressin (VP)- and phenylephrine
(PE)-induced responses were attenuated in both septic and ET-treated rats
for cytosolic and membrane proteins compared with their respective
controls. Glucagon and 12-O-myristate phorbol-13-acetate (TPA) affected
only the phosphorylation of membrane proteins. Glucagon-induced changes in
the phosphorylation of membrane proteins were affected by both sepsis and
endotoxicosis, whereas TPA-stimulated phosphorylation was lowered only in
endotoxicosis. Response to the Ca2+ ionophore A23187 was depressed in
septic rats for cytosolic proteins. The phosphorylation of two cytosolic
proteins, i.e., 93 and 61 kDa (previously identified as glycogen
phosphorylase and pyruvate kinase, respectively), in response to VP, PE,
and A23187 was severely impaired by endotoxicosis and sepsis. TPA did not
affect the phosphorylation state of these two proteins. The results show
that sepsis and endotoxicosis produce perturbations of the phosphorylation
step in Ca2+ transmembrane signaling. Such changes can explain alterations
of glycogenolysis and gluconeogenesis associated with sepsis and
endotoxicosis.
