547 HOMOGENEITY OF PHOSPHATE AND REDOX POTENTIALS IN THE SIMPLE LIVER ACINUS

Abstract

The microcirculatory or Rappaport model of the simple liver acinus is consistent with existing O2 concentration gradients which decrease from Zone 1 (arteriolar) to Zone 3 (venous), and which might impose gradients on oxidative energy metabolism. To test directly whether the intra-acinar O2 gradient manifests itself in corresponding gradients of phosphate and/or redox potential, quantitative histochemical methods and enzyme cycling were used together with oil well techniques and fluorometry to measure ATP, ADP, Pi, αglycerol-P (α GP) , and dihydroxy acetone-P (DHAP) in samples of acinar Zones 1 and 3 from normal and ischemic liver of ether anesthetized rats. Results are means ± SEM, mmol/kg dry weight. In the control state (Table), the parameters measured were the same in both Zones 1 and 3. During 30-150 seconds of ischemia, the phosphate potential (ATP/ADPxPi) fell and redox potential (αGP/DHAP) rose as expected. However, at no time did a difference develop between Zones 1 and 3. The data imply that, physiologically, O2 does not become a limiting factor for energy metabolism of the venous portion of the liver acinus. Zonal analysis is a sensitive means to test models of hepatic function. Supported by NIH grant #s 5P30AM19525-04 and AA03517-03.