The role of Ca2+ and hemodynamics in the action of diltiazem on hepatic energy metabolism

Metabolic effects of propofol in the isolated perfused rat liver

Inhibitory effects of the intravenous anaesthetic propofol on mitochondrial energy metabolism have been reported by several authors. Impairment of energy metabolism is usually coupled to reduction in ATP production, which in turn is expected to lead to several alterations in cell metabolism such as stimulation of glycolysis and inhibition of gluconeogenesis. The present work aimed at finding an answer to the question of how propofol affects energy metabolism-linked parameters in the isolated perfused rat liver. In the fed state, propofol increased glycogenolysis (glucose release), glycolysis (lactate and pyruvate production) and oxygen uptake in the range between 10 and 500 microM. In the liver of fasted rats, propofol up to 100 microM increased oxygen uptake but decreased gluconeogenesis from three different substrates: lactate, alanine and glycerol. When lactate was the substrate 50% inhibition occurred at a propofol concentration of 50 microM. Propofol (100 microM) decreased the ATP content of the liver (-33.3%), increased the AMP content (+25%) and decreased the ATP/ADP and ATP/AMP ratios (49 and 45%, respectively). Most effects of propofol are probably due to impairment of oxidative phosphorylation. Particularly, the combined differential action on oxygen uptake (stimulation) and gluconeogenesis (inhibition) is strongly suggestive of an uncoupling action also under the conditions of the intact cell. This effect, in turn, is consistent with the reported high affinity of the cellular hepatic structure, especially membranes, for propofol.

The action of oxybutynin on haemodynamics and metabolism in the perfused rat liver

The present study was planned to investigate the possible action of oxybutynin on liver haemodynamics and its influence on metabolic variables. The isolated liver perfused either bivascularly or monovascularly in the non-recirculating system was used for the experiments and Krebs/Henseleit-bicarbonate buffer (pH 7.4) as a perfusion fluid. Oxybutynin (25-200 microM) was infused, the infusion time for each concentration being 14 min. Portally infused oxybutynin increased the perfusion pressure starting at 100 microM. Oxygen uptake was diminished, also starting at 100 microM. Arterially infused oxybutynin also increased the perfusion pressure in the hepatic artery. Lactate and pyruvate releases were considerably diminished by oxybutynin. Glucose release showed a small initial stimulation, then returned to values slightly below the basal ones. Cessation of oxybutynin infusion resulted in progressive stimulation of glucose release. When Ca2+ was omitted all effects of oxybutynin vanished. The hepatic contents of glucose, glucose 6-phosphate and lactate in the presence of 200 microM oxybutynin increased 7.8-, 4.6- and 5.1 times, respectively. The pyruvate content was not changed. The ATP content was diminished by 26.6% in the presence of 200 microM oxybutynin, but the AMP content was increased by 64.3%. The ADP content was not changed. Apparently, upon administration of oxybutynin, a considerable fraction of the liver parenchyma ceased to be irrigated or almost so, which is apparent from the concomitant inhibition of oxygen uptake, pressure increase and inhibition of glucose, lactate and pyruvate release together with the simultaneous intracellular accumulation of glucose, lactate and glucose 6-phosphate.