Liu P, Hopfner RL, Xu YJ, Gopalakrishnan V. Vasopressin-evoked [Ca2+]i responses in neonatal rat cardiomyocytes.
J Cardiovasc Pharmacol 1999;
34:540-6. [PMID:
10511129 DOI:
10.1097/00005344-199910000-00010]
[Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The presence of arginine vasopressin (AVP) V1 receptors on neonatal rat cardiomyocytes (NRCs) linked to processes capable of elevating intracellular free calcium ([Ca2+]i) is now firmly established. This study examined the sources and signaling involved in [Ca2+]i elevations evoked by AVP in NRCs. AVP promoted increases in both [Ca2+]i and 1,4,5-inositoltrisphosphate (IP3) levels in NRCs. The degree of [Ca2+]i elevation was less than that of angiotensin II, but greater than that of endothelin-1. Extracellular Mg2+ depletion led to diminution of the maximal [Ca2+]i response, with a rightward shift in the concentration-response curves to AVP. The phospholipase C inhibitors, D-609, NCDC, or U73122, and the IP3 receptor blocker, heparin, abolished the [Ca2+]i response to AVP. Neither cyclooxygenase inhibition with indomethacin nor PKC inhibition with staurosporine had any effect. Neither ryanodine nor caffeine, which deplete sarcoplasmic reticulum (SR) Ca2+ stores, nor ruthenium red, which inhibits both SR and mitochondrial Ca2+ stores, affected [Ca2+]i responses to AVP. The SR Ca2+ pump inhibitor, cyclopiazonic acid, abolished, and removal of extracellular Ca2+ attenuated, the response to AVP. These data indicate that activation of cardiac V1 receptors by AVP results in mobilization of Ca2+ from a distinct, non-SR, nonmitochondrial, intracellular Ca2+ pool that is Ca2+ pump replenished and IP3 sensitive. This process occurs secondary to phospholipase C (PLC)-mediated generation of IP3, requires the presence of Mg2+ and extracellular Ca2+, and occurs in a manner independent of PKC and cyclooxygenase activation. Such mechanisms of Ca2+ mobilization might indicate a distinct role for AVP in cardiac physiology and disease.
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