%D 1993
%V 423
%A  VarrĂł AndrĂĄs
%A  Negretti N
%A  Hester SB
%A  Eisner David A
%T An estimate of the calcium content of the sarcoplasmic reticulum in rat ventricular myocytes
%N 1-2
%J PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
%I mi
%R MTMT:1132519 10.1007/BF00374975
%L publicatio32185
%X The aim of this paper was to estimate the Ca content of the
sarcoplasmic reticulum (s.r.) and to compare this with the amount of Ca
which enters the cell via the calcium current in systole. The s.r. Ca
content was measured electrophysiologically in voltage-clamped rat
ventricular myocytes. Rapid application of caffeine produced a
transient increase of [Ca2+]i which was accompanied by a transient
inward Na-Ca exchange current. The integral of this current gives a
measure of the Ca2+ pumped out of the cell by Na-Ca exchange. Ni2+ (5
mM) inhibited the current and decreased the rate of fall of [Ca2+]i to
32 % of the control suggesting that Na-Ca exchange is responsible for
68 % of Ca removal from the cytoplasm following the addition of
caffeine. Correcting for the Na-Ca independent Ca removal suggests that
the s.r. Ca content is equivalent to about 120 mumol per litre cell.
Furthermore we estimate that, during systole, Ca entry into the cell
via the sarcolemmal calcium current is equal to about 6 % of the Ca
content of the s.r.
%P 158-160