EXOGENOUS SUBSTRATES AS ENERGY-SOURCE FOR THE CONTRACTILE ACTIVITY OFTHE ISOLATED RAT TAIL ARTERY

The isolated rat tail artery underwent a pronounced depression of the contractile responses to adrenaline during the incubation in a glucose -free medium containing 2-deoxyglucose and/or oxfenicine in order to i nhibit the utilization of glycogen and/or endogenous triacylglycerol. When glucose was returned after 90 min of exposure to oxfenicine, the contraction strength recovered completely. In the;medium with 2-deoxyg lucose the addition of palmitate or hexanoate produced a recovery leve l 28 % and 16 % below the control values respectively. The effect of p almitate was nearly abolished and that of hexanoate partially decrease d in the medium containing both inhibitors. Under this condition pyruv ate reestablished the extent of the contraction to about 80 % of the c ontrol value whereas beta-hydroxybutyrate produced a weak and transien t recovery. These data suggest that in the tail artery the major porti on of the energy needed to sustain the contractile activity is supplie d by the oxidation of the more important plasmatic substrates with the exception of ketone bodies. However the Embden-Meyerhof pathway seems necessary to maintain at least a fraction of the contraction strength .