The hemodynamic effects of diltiazem in the isolated perfused rat liver are Ca(2+)-dependent

The action of zymosan on octanoate transport and metabolism in the isolated perfused rat liver

The effects of zymosan on transport, distribution, and metabolism of octanoate in the perfused rat liver were investigated using the multiple-indicator dilution technique. Livers were perfused with 300 microM octanoate in the absence or in the presence of 100 microg/mL zymosan. Tracer amounts of [1-14C]octanoate, [3H] water, and [131I]albumin were injected into the portal vein, and the effluent perfusate was fractionated. The normalized dilution curves were analyzed by means of a space-distributed variable transit time model. Zymosan decreased the space into which octanoate undergoes flow-limited distribution, possibly the first cellular exchanging pool represented by plasma membranes and their adjacencies. However, the rate of transfer of octanoate from the plasma membrane into the rest of the cell was not modified as indicated by the similar values of the influx rates and also the net uptake of octanoate per unit of accessible cellular volume. However, when referred to the wet weight of the liver, the net uptake of octanoate was 37.5% reduced, a value corresponding to the diminution of the cellular accessible space. It can be concluded that an exclusion of a fraction of the liver parenchyma from the microcirculation is the main mechanism by which zymosan reduces the metabolism of exogenous octanoate.

The hemodynamic effects of zymosan in the perfused rat liver

The actions of zymosan on hepatic microcirculation and on the cell membrane permeability were investigated using the multiple-indicator dilution technique. The experimental system was the perfused rat liver. [(3)H]Water, [(3)H]sucrose and [(14)C]urea or [(14)C]bicarbonate were simultaneously injected into the portal vein. Mean transit times, distribution spaces, variances, linear superpositions and transfer coefficients across the plasma membrane were calculated. Zymosan had no net effect on the great vessels space but increased the extracellular sucrose space and decreased the aqueous cell space. Zymosan impaired the flow-limited distribution and increased the normalized variances of all tracers. The increase in the portal pressure caused by zymosan results most probably from a constriction just after or at the exit of the sinusoids. Impairment of the flow-limited distribution of tracers in the sinusoidal bed indicates that zymosan induces the formation of permeability barriers, which could make the access of the solutes to transporters or enzymes located on the outer surface of the plasma membrane difficult.

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.