AJP - Cell Physiology, Vol 262, Issue 4 C941-C949, Copyright © 1992 by American Physiological Society
Activation of multiple mechanisms including phospholipase D by endothelin-1 in rat aorta
Y. Liu, B. Geisbuhler and A. W. Jones
Department of Physiology, School of Medicine, University of Missouri, Columbia 65212.
This study investigated the cellular mechanisms underlying the endothelin-1
(ET-1)-induced contraction of rat aorta with focus on the involvement of
phospholipase D (PLD). Preincubating rat aorta in Ca(2+)-free solution
reduced the contraction by 80%, whereas diltiazem (10 microM), a
voltage-operated Ca2+ channel blocker, caused only a small reduction (27%,
P less than 0.05) of the contraction. In myo-[3H]inositol-labeled aorta,
ET-1 stimulated the formation of [3H]inositol bisphosphate and [3H]inositol
trisphosphate, indicating the activation of phospholipase C (PLC). In aorta
labeled with 32PO4, [3H] myristic acid or [32P]lyso-platelet-activating
factor followed by exposure to ethanol (0.5%), ET-1 stimulated
phosphatidylethanol (PEt) production, suggesting that ET-1 activates PLD.
The PEt response was not attenuated by staurosporine (ST, 0.1 microM), an
inhibitor of protein kinase C (PKC) but was inhibited by removal of Ca2+.
The ET-1-induced PEt response was at least additive to that induced by
phorbol 12-myristate 13-acetate (1 microM). ET-1 also stimulated the
release of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) into the tissue
medium. Unlike the PEt responses, the 6-keto-PGF1 alpha response could be
inhibited by ST. Removal of Ca2+ abolished the response. These results
suggest that 1) ET-1 activates multiple cellular mechanisms including PLC,
PLD, and the arachidonate cascade; 2) PKC activation may not be essential
for the ET-1 activation of PLD but may play an important role in the ET-1
stimulation of 6-keto-PGF1 alpha release; and 3) Ca2+ is an important
factor in the ET-1-induced PLD activity and 6-keto-PGF1 alpha release.
