Comparison of Ca release and uptake characteristics of the sarcoplasmic reticulum in isolated horse and rabbit cardiomyocytes
نویسندگان
چکیده
Loughrey, C. M., G. L. Smith, and K. E. MacEachern. Comparison of Ca release and uptake characteristics of the sarcoplasmic reticulum in isolated horse and rabbit cardiomyocytes. Am J Physiol Heart Circ Physiol 287: H1149–H1159, 2004. First published April 29, 2004; 10.1152/ajpheart.00060.2004.—Both the cardiac action potential duration (APD) (0.6–1 s) and resting heart rate (30–40 beats/min) in the horse are significantly different from humans and smaller mammals, including the rabbit. This would be anticipated to have consequences for excitation-contraction (EC) coupling and require adaptation of the individual processes involved. The sarcoplasmic reticulum (SR) is one of the main components involved in EC coupling. This study examines and compares the activity of this organelle in the horse with that of the rabbit. In particular, the study focuses on SR Ca release via the Ca release channel/ryanodine receptor (RyR2) and Ca uptake via the sarco(endo)plasmic reticulum Ca -ATPase (SERCA) pump. Isolated cardiomyocytes from both horse and rabbit hearts were permeabilized, bathed in a mock intracellular solution, and exposed to a specified [Ca ]. Rabbit cardiomyocytes exposed to 260 nM [Ca ] produced spontaneous Ca release and propagated Ca waves. Horse cells failed to produce Ca waves; instead, only local release in the form of Ca sparks was evident. However, at 550 nM [Ca ], Ca waves were produced in both species. Ca waves were four times less frequent yet 1.5 times greater in amplitude in the horse compared with the rabbit. Ca wave velocity was comparable between the species. The reason for this disparity in Ca wave characteristics is unknown. Separate measurements of oxalate-supported Ca uptake into the SR suggest that both horse and rabbit cardiomyocytes have comparable levels SERCA activity. The possible reasons for the observed differences in SR Ca release between the horse and rabbit are discussed.
منابع مشابه
Comparison of Ca2+ release and uptake characteristics of the sarcoplasmic reticulum in isolated horse and rabbit cardiomyocytes.
Both the cardiac action potential duration (APD) (0.6-1 s) and resting heart rate (30-40 beats/min) in the horse are significantly different from humans and smaller mammals, including the rabbit. This would be anticipated to have consequences for excitation-contraction (EC) coupling and require adaptation of the individual processes involved. The sarcoplasmic reticulum (SR) is one of the main c...
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