Cardiovascular and renal effects of systemic hypoxia in chronically instrumented conscious WKY and SHR rats

The effects of systemic hypoxia upon cardiovascular and renal function in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) are controversial. We examined the effects of systemic normobaric hypoxia (12.5% O2 in N2 for 4 hours) on arterial blood gases (pO2, pCO2, pH), mean arterial pressure (MAP), heart rate (HR), effective renal blood flow (ERBF), glomerular filtration rate (GFR), urine flow (UMV) and renal sodium excretion (U Na V) in conscious unilaterally nephrectomized WKY (n = 12) and SHR (n = 14) chronically instrumented with an arterial, venous and ureter cannula. In WKY hypoxia caused a reduction in arterial pO2 and pCO2 but no change in MAP and HR. In SHR hypoxia induced similar reductions in arterial blood gases, a small decrease in MAP and no change in HR. In both strains hypoxia caused significant increases in ERBF, GFR and U Na V, but insignificant changes in UMV. The hypoxia-induced natriuresis developed 90-120 min after starting the hypoxia. These data indicate that a 4-hour lasting hypoxia has profound effects on sodium excretion in conscious WKY as well as SHR. Systemic hypoxia did not cause significant changes in arterial blood pressure in both rat strains.