Regulation of endothelin-mediated calcium mobilization in vascular smooth muscle cells by isoproterenol.


Journal Article

We have investigated the effect of isoproterenol on endothelin-induced Ca2+ mobilization in A10 vascular smooth muscle cells. Endothelin (ET) stimulates a rapid and sustained elevation of intracellular Ca2+ mediated by production of inositol phosphates, release of intracellular Ca2+, and activation of a plasmalemmal Ca2+ influx pathway. This influx pathway appears to be a L-type channel because it is inhibited by nicardipine and activated by BAY K 8644. Depolarization of the cells, by elevating extracellular K+, activated a pharmacologically similar channel and produced a similar change in intracellular Ca2+ concentration. Preincubation of cells with isoproterenol reduced the peak Ca2+ response to endothelin and blocked the sustained elevation. However, isoproterenol did not alter K(+)-induced Ca2+ entry. Thus it appears that ET-induced entry is mediated by intracellular signals and not by depolarization. With the use of cells incubated in Ca2(+)-free medium containing 1 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, isoproterenol was shown to inhibit Ca2+ release from intracellular pools by 36 +/- 3%. Furthermore, isoproterenol pretreatment or addition of adenosine 3',5'-cyclic monophosphate (cAMP) to saponin-permeabilized cells inhibited inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]-induced Ca2+ release from intracellular sites. Similar effects were seen with forskolin. Propranolol reversed the inhibitory effects of isoproterenol. Isoproterenol pretreatment also inhibited the rapid formation of Ins(1,4,5)P3 and [2-3H]inositol 1,3,4,5-tetrakisphosphate stimulated by endothelin and reduced the sustained formation of these compounds. Finally, isoproterenol and forskolin led to a greater than 10-fold increase in intracellular cAMP levels. This stimulation of adenylate cyclase by isoproterenol was completely blocked by propranolol. It appears then that the beta-agonist isoproterenol interacts with a beta-adrenergic receptor, elevates cAMP, and thereby alters endothelin-induced Ca2+ mobilization. Inhibition of Ins(1,4,5)P3 formation, reduction in the responsiveness of the Ins(1,4,5)P3 intracellular receptor, and perhaps inhibition of ET-induced Ca2+ entry appear to be involved.

Full Text

Cited Authors

  • Xuan, YT; Watkins, WD; Whorton, AR

Published Date

  • March 1, 1991

Published In

Volume / Issue

  • 260 / 3 Pt 1

Start / End Page

  • C492 - C502

PubMed ID

  • 1706144

Pubmed Central ID

  • 1706144

Electronic International Standard Serial Number (EISSN)

  • 2163-5773

International Standard Serial Number (ISSN)

  • 0002-9513

Digital Object Identifier (DOI)

  • 10.1152/ajpcell.1991.260.3.c492


  • eng