Sarcolemmal Alterations in Unloaded Rat Heart after Heterotopic Transplantation

Int J Angiol DOI: 10.1055/s-0038-1673646Following heterotopic transplantation, the rat heart undergoes atrophy and exhibits delayed cardiac relaxation without any changes in contraction and systolic Ca2+ transients. Furthermore, the sarcoplasmic reticular Ca2+ uptake and release activities were reduced and Ca2+ influx through L-type Ca2+ channels was increased in the atrophied heart. Since Ca2+ movements at sarcolemma are intimately involved in the regulation of intracellular Ca2+ concentration, the present study was undertaken to test if sarcolemma plays any role to maintain cardiac function in the atrophied heart.The characteristics of sarcolemmal Ca2+ pump and Na+–Ca2+ exchange activities were examined in 8 weeks heterotopically isotransplanted rat hearts which did not support hemodynamic load and underwent atrophy. Sarcolemmal ATP (adenosine triphosphate)-dependent Ca2+ uptake and Ca2+-stimulated ATPase (adenosine triphosphatase) activities were increased without any changes in Na+–K+ ATPase activities in the transplanted hearts. Although no alterations in the Na+-dependent Ca2+ uptake were evident, Na+-induced Ca2+ release was increased in the transplanted heart sarcolemmal vesicles. The increase in Na+-induced Ca2+ release was observed at different times of incubation as well as at 5, 20, and 40 mM Na+. The sarcolemma from transplanted hearts also showed higher contents of phosphatidic acid, sphingomyelin, and cholesterol.These results indicate that increases in t...
Source: International Journal of Angiology - Category: Cardiology Authors: Tags: Original Article Source Type: research