Details

Autor(en) / Beteiligte

• Loughrey, C. M
• Smith, G. L
• MacEachern, K. E

Titel

Comparison of Ca2+ release and uptake characteristics of the sarcoplasmic reticulum in isolated horse and rabbit cardiomyocytes

Ist Teil von

• American journal of physiology. Heart and circulatory physiology, 2004-09, Vol.287 (3), p.H1149-H1159

Ort / Verlag

United States

Erscheinungsjahr

2004

Quelle

MEDLINE

Beschreibungen/Notizen

• 1 Institute of Comparative Medicine, University of Glasgow Veterinary School, University of Glasgow, Glasgow G61 1QH; and 2 Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom Submitted 22 January 2004 ; accepted in final form 23 April 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 2+ release via the Ca 2+ release channel/ryanodine receptor (RyR2) and Ca 2+ uptake via the sarco(endo)plasmic reticulum Ca 2+ -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 2+ ]. Rabbit cardiomyocytes exposed to 260 nM [Ca 2+ ] produced spontaneous Ca 2+ release and propagated Ca 2+ waves. Horse cells failed to produce Ca 2+ waves; instead, only local release in the form of Ca 2+ sparks was evident. However, at 550 nM [Ca 2+ ], Ca 2+ waves were produced in both species. Ca 2+ waves were four times less frequent yet 1.5 times greater in amplitude in the horse compared with the rabbit. Ca 2+ wave velocity was comparable between the species. The reason for this disparity in Ca 2+ wave characteristics is unknown. Separate measurements of oxalate-supported Ca 2+ 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 2+ release between the horse and rabbit are discussed. cardiac; waves; equine Address for reprint requests and other correspondence: G. L. Smith, West Medical Bldg., Univ. of Glasgow, Glasgow G12 8QQ, UK (E-mail: g.smith{at}bio.gla.ac.uk ).