Effects of changes in PO2 and PCO2 and pH on the total vascular resistance of perfused cat kidneys

Abstract

The effects of change in arterial PO2, PCO2 and pH on the total vascular resistance (RVR) of the perfused cat kidney were separately measured and expressed as [plus or minus] percentage deviations from control values. Control levels in arterial blood were pH 7.38, P02 160 mm Hg, in equilibrium with 5% CO2. Increase in PO2 alone, in excess of 220 mm Hg, raised RVR reversibly reading 108% control levels at a PO2 280 mm Hg (P = < 0.001). High levels of PO2 favoured the onset of ''outflow block'', which was characterized by irreversible increase in RVR accompanied by rise in plasma filtration fraction (F.F.) and in the extraction ratio for p-aminohippuric acid (PAH extraction). Reduction in P02 to 80 mm Hg decreased RVR by 4% (P =< 0.001). RVR was not significantly affected by pH changes within the range 7.25-7.45. Lowering arterial pH to 7.15 raised RVR by 4% (p =< 0.001) reversibly. Increase in arterial pH to 7.56 raised RVR by 6% (P =< 0.001) reversibly. Changes in arterial PCO2 produced large inverse reversible changes in RVR. Halving PCO2 raised RVR by 18%J doubling PCO2 decreased RVR by 25%. Changes in RVR caused by alteration of arterial pH or PCO2 were not accompanied by changes either in F.F. or in PAH extraction.