ISSN:
1432-2013
Keywords:
Cardiac calcium channel
;
Xenopus oocyte
;
Protein kinase C
;
Phorbol esters
;
Diacylglycerol analog
;
Down-regulation
;
Intracellular Ca
;
cAMP
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract L-Type cardiac Ca2+ channels expressed in Xenopus oocyte were studied following rat heart ribonucleic acid, messenger (mRNA) injection. We demonstrate that exogenous Ca2+ channels are sensitive to intracellular regulation by protein kinase C (PKC). This was performed by using two types of PKC activators [phorbol esters and a structural analogue of diacylglycerol (DAG)] and a specific peptidic inhibitor. Ca2+ channel modulation resulted in an initial increase of the inward current, without any modification of the voltage-dependent properties, and a second delayed phase, specifically observed with phorbol esters, characterized by a progressive decrease in current amplitude. Concomitantly, a reduction of membrane capacitance, reflecting a reduction of the total membrane surface area, was observed. We suggest that this phenomenon underlies the irreversible decrease of the expressed Ba2+ current via sequestration of Ca2+ channels and/or PKC. We also demonstrate that regulation of cardiac mRNA-directed Ca2+ channels by PKC activators was strictly dependent on intracellular Ca2+ concentration, and was partially additive with cyclic-adenosine-monophosphate-(cAMP) dependent regulation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374834
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