M. Thibonnier et al., ROLE OF EICOSANOIDS IN VASOPRESSIN-INDUCED CALCIUM MOBILIZATION IN A7R5 VASCULAR SMOOTH-MUSCLE CELLS, The American journal of physiology, 265(1), 1993, pp. 50000108-50000114
The role of arachidonic acid (AA) and its metabolites in vasopressin (
AVP)-induced calcium mobilization in A7r5 aortic smooth muscle cells w
as explored by intracellular calcium monitoring, [C-14]AA labeling, an
d high-performance liquid chromatography (HPLC) techniques. In fura 2-
loaded A7r5 cells, AA potentiated AVP-stimulated increase in intracell
ular free Ca2+ ([Ca2+]i). The cyclooxygenase inhibitor indomethacin re
duced both the AA- and AVP-induced influx of extracellular Ca2+. AVP-i
nduced [Ca2+], transients were not altered by lipoxygenase inhibitors
but were reduced in a dose-dependent fashion by ketoconazole, an inhib
itor of cytochrome P-450 monooxygenases. Among several epoxygenase met
abolites of AA tested, 5,6-epoxyeicosatrienoic acid potentiated AVP-in
duced [Ca2+]i transients. Reverse-phase HPLC analysis of lipid extract
s from A7r5 cells prelabeled with [C-14]AA isolated a radioactive peak
that did not coelute with established products of cyclooxygenase-, li
poxygenase-, or cytochrome P-450-catalyzed oxidations of AA. This peak
was significantly increased after AVP stimulation and was completely
blocked by preincubation with ketoconazole. Thus the stimulation of V1
-vascular AVP receptors of A7r5 cells triggers several cytoplasmic sig
naling pathways involving AA metabolite formation through the cyclooxy
genase and epoxygenase pathways.