© 2001 by European Society of Cardiology
Copyright © 2000, European Society of Cardiology
Calcium buffering in coronary smooth muscle after chronic occlusion and exercise training
Vascular Biology Laboratory, Dalton Cardiovascular Research Center, and Department of Physiology, University of Missouri, Columbia, MO 65211, USA
* Corresponding author. Present address: Department of Physiology, MA415 Medical Sciences Building, School of Medicine, University of Missouri, Columbia, MO 65212, USA. Tel.: +1-573-882-2640; fax: +1-573-884-4232 sturekm{at}missouri.edu
Objective: Exercise promotes "sarcoplasmic reticulum (SR) Ca2+ unloading" in porcine coronary smooth muscle, resulting in decreased agonist-induced Ca2+ release. We studied Ca2+ handling in healthy, non-occluded right coronary artery cells from hearts chronically occluded at the circumflex artery. Methods: Myoplasmic free Ca2+ (Cam) was assessed with fura-2 in cells from sedentary (n=8) and aerobically exercise-trained (n=6) female Yucatan pigs after 6-month circumflex artery ameroid occlusion (OCC) and in cells from non-occluded, sedentary pigs (SED, n=5). First, Ca influx was induced by 80 mM KCl depolarization (priming step) followed by 5 mM caffeine to elicit maximal Ca2+ release and depletion. The SR was Ca-loaded again by depolarization and then exposed to caffeine after 2- or 11-min recovery to compare SR Ca2+ unloading. Results: Baseline Cam, caffeine-induced peak Cam, and depolarization-induced maximum Cam were decreased, and depolarization-induced time-to-half-maximum was increased in OCC vs. SED pigs, suggesting a tonic Ca2+ buffering (lowering) effect of occlusion. Exercise did not alter these effects. SR Ca2+ unloading occurred only in SED, as evidenced by decreased caffeine-induced Ca2+ release after 11 min of recovery, and was inhibited by low extracellular Na+. Conclusions: SR Ca2+ unloading can be demonstrated in coronary smooth muscle from sedentary pigs using a novel SR Ca2+ unloading protocol, and Ca2+ unloading partly depends on Na+–Ca2+ exchange activity. Furthermore, SR Ca2+ unloading in cells from non-occluded right coronary arteries of chronically circumflex-occluded pig hearts was not altered by exercise, perhaps due to enhanced tonic Ca2+ extrusion versus cells from normal, sedentary animals.
KEYWORDS Calcium (cellular); Collateral circulation; Coronary circulation; Coronary disease; Na/Ca-exchanger; SR (function)
1 Current addresses of authors who have moved since the work was finished: Janet L. Parker, Ph.D., Department of Medical Physiology, Joe H. Reynolds Building, Texas A & M University, College Station, TX 77843-1114, USA. Cristine L. Heaps, Ph.D., Veterinary Biomedical Sciences, E102 Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. M. Lawler, H.-B. Kwak, W. Song, and J. L. Parker Exercise training reverses downregulation of HSP70 and antioxidant enzymes in porcine skeletal muscle after chronic coronary artery occlusion Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2006; 291(6): R1756 - R1763. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. L. Heaps, M. L. Mattox, K. A. Kelly, C. J. Meininger, and J. L. Parker Exercise training increases basal tone in arterioles distal to chronic coronary occlusion Am J Physiol Heart Circ Physiol, March 1, 2006; 290(3): H1128 - H1135. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. A. Mokelke, N. J. Dietz, D. M. Eckman, M. T. Nelson, and M. Sturek Diabetic dyslipidemia and exercise affect coronary tone and differential regulation of conduit and microvessel K+ current Am J Physiol Heart Circ Physiol, March 1, 2005; 288(3): H1233 - H1241. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Cao, M. D. Vrees, M. T. Kirber, C. Fiocchi, and V. E. Pricolo Hydrogen peroxide contributes to motor dysfunction in ulcerative colitis Am J Physiol Gastrointest Liver Physiol, May 1, 2004; 286(5): G833 - G843. [Abstract] [Full Text] [PDF]
|
|