Exercise training alters the Ca2+ and contractile responses of coronary arteries to endothelin.
We tested the hypothesis that alterations in myoplasmic free Ca2+ (Ca(m)) regulation in coronary smooth muscle after exercise training (Ex) underlie changes in vasomotor function. Yucatan miniature pigs were endurance trained by treadmill running for 16-20 wk. Simultaneous determination of Ca(m) (fura-2 microfluorometry) and contraction during endothelin exposure in coronary arteries were then performed. Endothelin (10(-9) to 10(-7) M) was administered either cumulatively or as a single concentration. Ex significantly attenuated the Ca(m) response to 10(-9) and 10(-8) M endothelin. Developed tension was significantly diminished at 10(-8) M endothelin in Ex pigs, producing a rightward shift in the concentration-developed tension response. Attenuated Ca(m) and contractile response to 10(-8) M endothelin were present after Ex whether endothelin was applied cumulatively or as a single concentration. The developed tension-Ca(m) relationship showed an increased Ca(m) sensitivity of contraction with Ex. Endothelin (10(-8) M)-induced Ca2+ influx, estimated by Ba2+ influx in low-Na+ solution, was increased threefold in coronary arteries from Ex pigs. The decreased Ca(m) in the presence of increased divalent cation (i.e., Ca2+) influx during 10(-8) M endothelin suggests a greatly enhanced sarcolemmal Ca2+ cycling in coronary arteries from Ex pigs.
Bowles
D K
DK
Dalton Cardiovascular Research Center, Department of Physiology, University of Missouri, Columbia 65211, USA.
Laughlin
M H
MH
Sturek
M
M
D000818:Animals; D001158:Arteries / Q000187:drug effects; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D003331:Coronary Vessels / Q000187:drug effects*; D016232:Endothelins / Q000494:pharmacology*; D005260:Female; D010805:Physical Conditioning, Animal; D013552:Swine; D013556:Swine, Miniature; D014661:Vasoconstriction / Q000187:drug effects*
D016232:Endothelins; D001464:Barium; D002118:Calcium