Calcium as a Hormonal Messenger for Control of Mitochondrial Functions

Abstract

During the past decade it has become generally accepted that hormones such as norepinephrine, angiotensin II, and vasopressin affect metabolism of the rat liver by increasing free calcium [Ca²⁺ ] of the cytosol. In contrast, a role for calcium as a mediator of the action of glucagon has been controversial. Reports that glucagon alters fluxes of calcium in and out of the liver cell and that it lowers mitochondrial calcium were nullified to some degree by other reports indicating that these effects were observed only when pharmacological doses of glucagon were administered and that cytosolic [Ca²⁺ ] is not altered by glucagon. The unsettled nature of the field was described in the comprehensive review of Williamsonet al. (1981). Things began to fall into place when the fluorescent probe for [Ca²⁺ ], Quin2, became available, and Charestet al. (1983) demonstrated that glucagon added at the high ose level of 10 nM raised cytosolic [Ca²⁺ ] of hepatocytes from a basal concentration of about 0.2µM to 0.6µM.