To obtain a reasonable estimate in vivo of the liver extracellular space (ECS) in intact, non-exsanguinated dogs, the distribution volumes of a variety of radioactive tracers were obtained as a function of time. 36Cl, 14C- and 3H-inulin, 125I-albumin, 51Cr-red cells, and endogenous 35Cl distribution volumes were obtained in liver from 5 min to 4 h. The 36Cl space was stable and reproducible at 29.0%, a value similar to the endogenous 35Cl (28.2%) and 5 min 14C-inulin (29.9%) spaces. The 36Cl space may be used as the upper limit of liver ECS, whereas the inulin space exceeds this value after 5 min and progressively increases. Electrolyte concentrations in liver cell water are calculated using the 36Cl space of 29% as the liver ECS. The advantages of using 36Cl over other methods to determine liver ECS in intact animals are discussed.
Simultaneous measurements of hemodynamics, arterioventricular (AV) conduction, and renal functioner were obtained in conscious dogs. Catheters were implanted for the long-term measurement of central aortic, right ventricular, and pulmonary artery pressure. AV conduction was assessed following surgical implantation of multipolar electrode plaques in the area of the bundle of His, as well as on the epicardium of the right and left atria and ventricles. Renal function was assessed utilizing standard techniques. Following control measurements, lidocaine, 1 mg/kg, or procaine amide, 10 mg/kg, was administered intravenously. Subsequently, serial measurements were obtained for a 90-min period. No significant changes in hemodynamics were observed following either drug. Procaine amide produced a significant increase in heart rate and a minimal increase in QRS duration associated with a decrease in low right atrial to His bundle conduction time. However, no significant changes in cardiac conduction were observed after lidocaine administration. Renal function was unaffected by lidocaine but significantly depressed by procaine amide, as demonstrated by a decrease in GFR and effective renal flow. In summary, acute administration of procaine amide significantly alters renal function in the conscious dog with minimal effects on AV conduction and hemodynamics.
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