Changes in activity and regulation of the cardiac Ca2+ channel (L-type) byprotein kinase C in chronic alcohol-exposed rats

Citation
M. Solem et al., Changes in activity and regulation of the cardiac Ca2+ channel (L-type) byprotein kinase C in chronic alcohol-exposed rats, ALC CLIN EX, 24(8), 2000, pp. 1145-1152
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Clinical Psycology & Psychiatry","Neurosciences & Behavoir
Journal title
ALCOHOLISM-CLINICAL AND EXPERIMENTAL RESEARCH
ISSN journal
0145-6008 → ACNP
Volume
24
Issue
8
Year of publication
2000
Pages
1145 - 1152
Database
ISI
SICI code
0145-6008(200008)24:8<1145:CIAARO>2.0.ZU;2-X
Abstract
Background: It has been reported recently that long-term alcohol exposure i n rats increases the number of dihydropyridine binding sites in cardiac mem brane preparations. We fed Sprague Dawley((R)) rats a liquid diet that cont ained ethanol as 36% of total calories for 4 to 6 months and studied how al cohol exposure affected the activity and regulation of the cardiac Ca2+ cha nnel. Methods: Dihydropyridine-sensitive cardiac Ca2+ channel activity was measur ed as the rate of Mn2+ quench of the cytosolic fura-2 signal in electricall y stimulated myocytes. Results: In control rat myocytes, pretreatment with phorbol 12-myristate 13 -acetate (PMA), an activator of protein kinase C (PKC), reduced the rate of Mn2+ quench to 68% of the untreated cell response. Pretreatment with GF109 203X, a protein kinase C inhibitor, enhanced the rate of influx by 56%, whe reas Go6976, an inhibitor of PKC alpha, beta, and gamma, did not affect the rate of influx. By contrast, PMA did not affect the rate of Mn2+ quench in alcoholic myocytes; however, the PKC inhibitor GF109203X still enhanced th e rate of Mn2+ quench by 33%. Similar to control myocytes, no effect was ob served after pretreatment with Go6976 in the alcoholic cells. In both Weste rn blot and immunoprecpitation experiments, PKC epsilon expression in alcoh ol-exposed myocytes was reduced to 68% of the control. However, the ratio o f membrane/ cytosolic distribution of PKC epsilon in alcoholic myocytes was increased from 1.6 to 2.6. No change was detected in the expression of PKC alpha and PKC delta. PKC activity, measured in the presence of Go6976, whi ch inhibits PKC alpha, beta, and gamma, was reduced in alcoholic myocytes t o 57% of the control, but the proportion of PKC activity in the particulate fraction was increased from 26% in the control myocytes to 36% in the alco holic myocytes. Conclusions: Altered expression and activity of PKC may be associated with changes in the regulation of the cardiac Ca2+ channel found in the hearts o f rats chronically exposed to alcohol. Specifically, we found that the nove l class of PKC isozymes is responsible for regulating the cardiac Ca2+ chan nel in control cardiomyocytes, and that the loss of PMA modulation found in the alcoholic cells may be due, in part, to reduced expression and altered distribution of PKC epsilon.