Hormone-induced changes in NADH fluorescence and O2 consumption of rat hepatocytes.

Hepatocytes isolated from fasted male rats were incubated with a mixture of glucose, ribose, mannose, glycerol, and acetate and then treated with vasopressin (ADH), glucagon, or vasoactive intestinal polypeptide (VIP). Each of these hormones causes a rapid transient increase in the fluorescence signal arising from NADH and a sustained increase in the rate of metabolic oxygen consumption (QO2). The NADH transient was largest in response to glucagon, followed by ADH and VIP, respectively. For each hormone the responses were prevented by addition of a calcium-chelating agent. These results show that a transient, Ca2+-dependent redox shift in NADH and stimulation of QO2, perhaps resulting from an increase in the rate of delivery of reducing equivalents to the mitochondrion, occur early in the sequence of events by which several hormones that increase gluconeogenesis act.