The relative contributions of different intracellular and sarcolemmal systems to relaxation in rat ventricular myocytes.
Cardiovasc Res
; 27(10): 1826-30, 1993 Oct.
Article
em En
| MEDLINE
| ID: mdl-8275530
ABSTRACT
OBJECTIVE:
The aim was to estimate the relative contributions of the various intracellular and sarcolemmal systems to the relaxation of the systolic calcium transient.METHODS:
The experiments were performed on isolated rat ventricular myocytes. The cells were loaded with the fluorescent indicator indo-1 in order to measure [Ca2+]i.RESULTS:
The application of caffeine to release calcium from the sarcoplasmic reticulum produced a rise of [Ca2+]i which decayed about 7-8 times more slowly than the electrically stimulated calcium transient. This suggests that the sarcoplasmic reticulum accounts for about 87% of the calcium removal. The rate of decay of the caffeine response was decreased to about 33% of the control by inhibiting the Na-Ca exchange with Ni2+. In the presence of Ni2+ the rate could be inhibited further by inhibiting either the sarcolemmal Ca-ATPase (by increasing extracellular calcium concentration, [Ca2+]o) or the mitochondria (with FCCP and oligomycin). The relative contributions of the various processes were estimated to be sarcoplasmic reticulum 87%, mitochondria 1.7%, Na-Ca 8.7%, sarcolemmal Ca-ATPase 2.6%.CONCLUSIONS:
These experiments show that the Na-Ca exchange accounts for 67% of the calcium removal not mediated by the sarcoplasmic reticulum. This is a smaller fraction than in rabbit cardiac cells and highlights the importance of the Ca-ATPase in the rat heart.
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Base de dados:
MEDLINE
Assunto principal:
Sarcolema
/
Retículo Sarcoplasmático
/
Cálcio
/
Líquido Intracelular
/
Contração Miocárdica
Limite:
Animals
Idioma:
En
Ano de publicação:
1993
Tipo de documento:
Article