Regulation of calcium transport in drug-induced taurine-depleted hearts.
Drug-induced taurine depletion of rat heart led to the accumulation of free CoA, free carnitine and long-chain acylcarnitine, but a small decrease in long-chain fatty acyl-CoA. Although elevations in total tissue long-chain acylcarnitine levels have been linked to defective membrane function and the association of long-chain acylcarnitines with extramitochondrial membranes, these effects were absent in isolated sarcoplasmic reticulum prepared from taurine-depleted hearts. In contrast to the sarcoplasmic reticulum data, taurine depletion was associated with a significant decrease in ATP-dependent calcium uptake by isolated sarcolemmal vesicles. The major effect of taurine depletion on the sarcolemma was a 2-fold decrease in both the Vmax of calcium transport and the activity of the Ca2+ -stimulated ATPase. Sarcolemmal vesicles prepared from taurine-depleted hearts also exhibited a decreased capacity to transport calcium in exchange for sodium, although the initial rate of the process was unaffected by taurine depletion. Since incubation of sarcolemma from taurine-depleted hearts with taurine could not overcome the effects of taurine depletion, it was concluded that the effects of taurine were not caused by a direct interaction of it with the calcium pump. Possible mechanisms of taurine action are discussed.
Harada
H
H
University of South Alabama, School of Medicine, Department of Pharmacology, Mobile 36688.
Allo
S
S
Viyuoh
N
N
Azuma
J
J
Takahashi
K
K
Schaffer
S W
SW
D000818:Animals; D001693:Biological Transport, Active; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000493:pharmacokinetics*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002331:Carnitine / Q000378:metabolism; D003065:Coenzyme A / Q000378:metabolism; D006706:Homeostasis; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D013654:Taurine / Q000502:physiology*
D013654:Taurine; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002331:Carnitine; D003065:Coenzyme A; D002118:Calcium