Oxygen and glucose withdrawal on portal veins: NADH fluorescence and spontaneous activity

Parallel with the spontaneous mechanical activity, changes in steady-state levels of reduced pyridine nucleotides (PN) of rat portal veins were recorded by continuous monitoring of surface fluorescence. These data were correlated with changes in tissue concentrations of glucose, lactate and ATP when subjected to long-term anoxia and/or glucose depletion. In response to anoxia and addition of glucose the fluorescence intensity excited at 366 nm increased, representing a reduction of PN. This was accompanied by a higher tissue lactate content. Spontaneous contraction force decreased independently of accelerated glycolysis, which did not compensate for eliminated oxidative metabolism. The frequency of spontaneous contractions changed time-dependent. When O2 was added after more than 3 h of anoxia the spontaneous activity was restituted and PN were re-oxidized. Contraction relaxation cycles of spontaneous activity were accompanied by phasic changes of PN fluorescence clearly detectable in vessels supplied with glucose only. Suppressive effects of O2 and/or glucose depletion upon spontaneous contractile activity seem to be mediated more by alterations of cell membrane properties than by changes in energy metabolism.