Ca transport and heat production in vesicles derived from the sarcoplasmic reticulum terminal cisternae: Regulation by K |
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Authors: | Mariana Nigro Leopoldo de Meis |
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Institution: | Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Cidade Universitária, RJ, 21941-902, Brazil |
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Abstract: | In this work, we compared the effect of K+ on vesicles derived from the longitudinal (LSR) and terminal cisternae (HSR) of rabbit white muscle. In HSR, K+ was found to inhibit both the Ca2+ accumulation and the heat released during ATP hydrolysis by the Ca2+-ATPase (SERCA1). This was not observed in LSR. Valinomycin abolished the HSR Ca2+-uptake inhibition promoted by physiological K+ concentrations, but it did not modify the thermogenic activity of the Ca2+ pump. The results with HSR are difficult to interpret, assuming that a single K+ is binding to either the ryanodine channel or to the Ca2+-ATPase. It is suggested that an increase of K+ in the assay medium alters the interactions among the various proteins found in HSR, thus modifying the properties of both the ryanodine channel and SERCA1. |
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Keywords: | Heat production Ca2+-ATPase Thermogenesis Heavy sarcoplasmic reticulum Light sarcoplasmic reticulum |
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