title: Alterations in calcium stores in aortic myocytes from spontaneously hypertensive rats.
abstract: The aim of the present work was to further characterize intracellular calcium stores released by angiotensin II (Ang II) in spontaneously hypertensive rat (SHR) and Wistar-Kyoto rat (WKY) vascular smooth muscle cells (VSMCs) and to study their alterations associated with proliferation. Intracellular Ca2+ concentration was monitored by image analysis in aortic myocytes loaded with fura 2. In the presence of extracellular Ca2+, sensitivity to Ang II in proliferating VSMCs was not different in the two strains, but it increased 10-fold in confluent VSMCs from SHR-compared with those from WKY. In Ca(2)+-free medium, Ca2+ release induced by thapsigargin (10 mumol/L) was significantly greater (about twofold) in SHR than WKY, in both proliferating and confluent cultures, with responses during proliferation being 0.7-fold smaller. Responses to Ang II were abolished after exposure of the cells to thapsigargin. In proliferating cultures, ryanodine (10 mumol/L) did not modify the rises in intracellular Ca2+ concentration induced by Ang II in VSMCs from both strains. Conversely, in confluent cultures, ryanodine reduced Ang II (100 nmol/L)-induced Ca2+ release to the same level as in proliferating cultures, and it suppressed the difference between SHR and WKY. These results show that the ryanodine-sensitive Ca2+ release induced by Ang II is enhanced in VSMCs from SHR at confluence and is impaired during proliferation. Thus, they suggest that differences in Ca2+(-)induced Ca2+ release from the sarcoplasmic reticulum may participate in increased responsiveness of VSMCs to Ang II in SHR and in phenotypic modulation of vascular myocytes during proliferation.
authors.affiliation: Laboratoire de Pharmacologie et Physiopathologie Cellulaires, Université Louis Pasteur de Strasbourg URA CNRS 600, Faculté de Pharmacie, Illkirch, France.
authors.forename: S F
authors.initials: SF
authors.lastname: Côrtes
authors.forename: V S
authors.initials: VS
authors.lastname: Lemos
authors.forename: J C
authors.initials: JC
authors.lastname: Stoclet
mesh_terms: D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012433:Ryanodine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D000804:Angiotensin II; D012433:Ryanodine; D019284:Thapsigargin; D002118:Calcium