Sodium-induced calcium release from mitochondria in brown adipose tissue.

Abstract

Coupled mitochondria of [hamster] brown adipose tissue can accumulate Ca2+ if a substrate is present. The Ca2+ is released by addition of 20 mM Na+, but not by addition of K+ or choline+. Energy-dissipating Na+ induced Ca2+ cycling occurs maximally with 20 mM Na+ and 10 .mu.M Ca2+. In brown adipocytes, the Ca2+ionophore A23187 and the Na+ ionophore monensin increase respiration if substrate is added and incubation in a low-Na+ buffer decreases norepinephrine induced respiration. The Na+ induced Ca2+ release takes place in brown adipose tissue; released Ca2+ could have a regulatory or thermogenic role or both.