AJP - Endocrinology and Metabolism, Vol 264, Issue 3 E465-E470, Copyright © 1993 by American Physiological Society
LPS inhibits PI-phospholipase C but not PC-phospholipase D or phosphorylase activation by vasopressin and norepinephrine
R. A. Pittner and J. A. Spitzer
Department of Physiology, Louisiana State University Medical Center, New Orleans 70112-1391.
Rats were infused with endotoxin (50 micrograms/100 g body wt) for 3 h, and
the parenchymal cells of the liver were maintained in primary culture for
1-3 h. The effects of vasopressin, norepinephrine, and glucagon on the
activation of phosphatidylinositol (PI)-phospholipase C,
phosphatidylcholine (PC)-phospholipase D, and glycogen phosphorylase a were
investigated. Activation of PI-phospholipase C was markedly reduced,
particularly with norepinephrine. This confirms that one of the early
metabolic impairments seen in acute endotoxin treatment is inhibition of
PI-phospholipase C activity. However, the ability of vasopressin,
norepinephrine, and glucagon to stimulate glycogen phosphorylase a and
PC-phospholipase D was not affected by this endotoxin treatment. We
conclude that activation of phosphorylase a by vasopressin and
norepinephrine is not entirely dependent on the activation of
PI-phospholipase C and inositol trisphosphate formation.
