Toxicokinetic modeling of dose-dependent formate elimination in rats: in vivo-in vitro correlations using the perfused rat liver

The dose-dependent elimination of formate was investigated in the rat using both in vitro and in vivo systems. The in situ perfused liver was used to define the kinetics of hepatic metabolism and obtain initial in vitro estimates of the hepatic metabolism kinetic parameters. Formate was eliminated from the perfused rat liver following Michaelis-Menten kinetics. Estimates of the Michaelis-Menten parameters obtained from the perfused liver studies were used in a two-compartment pharmacokinetic model of the dose-dependent elimination of formate in vivo. This model consisted of a central, well-mixed compartment and a urine compartment. Other features of the model included (1) endogenous production of formate, (2) Michaelis-Menten hepatic metabolism of formate, and (3) renal excretion consisting primarily of glomerular filtration and saturable tubular reabsorption. A good fit of the model to the observed in vivo data was obtained (overall r2 = 0.978). AR dose dependencies of the data could be adequately fitted using a single set of model parameters. Initial estimates of the Michaelis-Menten parameters, Vmax and Km, obtained from the perfused liver system, were within 40% of the final fitted values of these parameters in the in vivo model, indicating the utility of the perfused liver system for performing in vitro-in vivo correlations.

[Problems with anesthesia and intensive therapy in pheochromocytoma. A review of 25 cases]

A retrospective assessment is made of 25 cases of pheochromocytoma operated between 1970 and 1979. Three of the more complicated cases are discussed in detail. Actual and potential complications are described and a form of monitoring is proposed. The conclusion is expressed that correction of the pathological haemodynamic situation by expansion of the blood volume and the administration of alpha and beta blocking agents is of greater consequence in successful management than the anaesthesiological technique employed.