Ca2+ transport and heat production in vesicles derived from the sarcoplasmic reticulum terminal cisternae: regulation by K+.
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.
Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Cidade Universitária, RJ, 21941-902, Brazil.
Mariana
M
Nigro
Ana Paula
AP
Arruda
Leopoldo
L
de Meis
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D006358:Hot Temperature; D006868:Hydrolysis; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism
D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium