3-HYDROXYBUTYRATE CO-INFUSED WITH NORADRENALINE DECREASES RESULTING PLASMA-LEVELS OF NORADRENALINE IN WISTAR RATS

Pentobarbital-anaesthetized male Wistar rats were infused with 6 mu g kg(-1) min(-1) of noradrenaline, The infusion was supplemented with 8. 5 mg kg(-1) min(-1) of D-3-hydroxybutyrate (3-OHB) for 15 min in order to determine its effect on the adrenergic response of the rat, Plasma levels of noradrenaline rose to a plateau of approximately 50 nmol l( -1) with infusion, In the group infused with noradrenaline alone, nora drenaline levels were maintained for Ih, Supplementation with 3-OHB in duced a decrease in plasma noradrenaline level that was inversely corr elated with 3-OHB level, Aortic and interscapular brown adipose tissue temperatures increased with noradrenaline infusion, but the rise was arrested by 3-OHB; replacing 3-OHB with glucose had no effect, Infusio n of saline, glucose or 3-OHB in the absence of noradrenaline did not induce a rise in temperature in either tissue, Blood 3-OHB concentrati on increased to 1.2 mmol l(-1) during 3-OHB infusion, decreasing rapid ly at the end of infusion, Blood glucose levels increased with noradre naline infusion; the presence of high 3-OHB levels decreased glucose c oncentration, The effects observed were transient and dependent on 3-O HB concentration; these effects may help explain most of the other eff ects of noradrenaline described here, The role of 3-OHB as a regulator of adrenergic responses seems to be part of a complex fail-safe mecha nism which prevents wasting.