TY - JOUR
T1 - The enhancement of Ca2+ efflux from sarcoplasmic reticulum vesicles by urea
AU - Chini, Eduardo Nunes
AU - de Faria, Felipe Oliveira
AU - Cardoso, Cristiana M.
AU - de Meis, Leopoldo
N1 - Funding Information:
This investigation was supported by Financiadora de Estudos e Pro-jetos, Conselho National de Desesnvolvimento Cientifico e Tecnologico (CNPq), and by Fundacao de Amparo a Pesquisa do Rio de Janeiro. E. N. Chini, F. 0. de Faria, and C. M. Cardoso are recipients of fellowships from CNPq. We thank Frederic0 G. Steidel de Toledo, Isabela Teixeira e Borges, and Vivian Barral Dodd Rumjanek for helpful discussions of the manuscript. Excellent technical assistance was provided by Geovano Santos de Fonseca.
PY - 1992/11/15
Y1 - 1992/11/15
N2 - Urea, in nondenaturing concentrations, inhibited Ca2+ uptake by sarcoplasmic reticulum vesicles with no concomitant effect on ATP hydrolysis. This inhibition was antagonized by 5 mm oxalate and 20 mm orthophosphate. At concentrations of 0.2 to 1.0 m, urea induced an increase in the Ca2+ efflux from preloaded vesicles diluted in a medium at pH 7.0 containing 2 mm ethylene glycol bis(β-aminoethyl ether)N,N′-tetraacetic acid, 0.1 mm orthophosphate, and 0.1 mm MgCl2. The urea-induced efflux was arrested by ligands of the (Ca2+-Mg2+) ATPase, namely, K+, Mg2+, Ca2+, and ADP, and by ruthenium red and the polyamines spermine, spermidine, and putrescine. In the case of polyamines a dissociation between the effect on the efflux and the net Ca2+ uptake was observed, as only the efflux could be blocked by the drugs. Glycine betaine, trimethylamine-N-oxide, and sucrose antagonized the effects of urea on both the net Ca2+ uptake and the rate of Ca2+ efflux.
AB - Urea, in nondenaturing concentrations, inhibited Ca2+ uptake by sarcoplasmic reticulum vesicles with no concomitant effect on ATP hydrolysis. This inhibition was antagonized by 5 mm oxalate and 20 mm orthophosphate. At concentrations of 0.2 to 1.0 m, urea induced an increase in the Ca2+ efflux from preloaded vesicles diluted in a medium at pH 7.0 containing 2 mm ethylene glycol bis(β-aminoethyl ether)N,N′-tetraacetic acid, 0.1 mm orthophosphate, and 0.1 mm MgCl2. The urea-induced efflux was arrested by ligands of the (Ca2+-Mg2+) ATPase, namely, K+, Mg2+, Ca2+, and ADP, and by ruthenium red and the polyamines spermine, spermidine, and putrescine. In the case of polyamines a dissociation between the effect on the efflux and the net Ca2+ uptake was observed, as only the efflux could be blocked by the drugs. Glycine betaine, trimethylamine-N-oxide, and sucrose antagonized the effects of urea on both the net Ca2+ uptake and the rate of Ca2+ efflux.
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U2 - 10.1016/0003-9861(92)90245-R
DO - 10.1016/0003-9861(92)90245-R
M3 - Article
C2 - 1280064
AN - SCOPUS:0026613356
SN - 0003-9861
VL - 299
SP - 73
EP - 76
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 1
ER -