Cellular events underlying catecholamine-induced thermogenesis: cation transport in brown adipocytes.

Evidence supporting the hypothesis that the active transport of Na+ and K+ contributes significantly to catecholamine-mediated brown fat thermogenesis is reviewed. Such evidence indicates that the Na+/K+ membrane pump is activated following norepinephrine interaction with alpha- and beta-adrenergic membrane receptors. That the involvement of the pump in the thermogenic response is considerable is indicated by the finding that pump inhibition is accompanied by a 50--70% reduction of the catecholamine-evoked respiratory stimulation of isolated hamster brown adipocytes. This inhibitory effect of pump blockade suggests that in the norepinephrine-activated brown adipocyte, the pump generates a stimulatory signal for pathways of substrate oxidation, the operation of these being associated with conversion of chemical energy to heat.