Effects of chronic changes in hemoglobin-O2 affinity in rats

Abstract

We have assessed the characteristics of oxygen transport following chronic intraperitoneal administration of sodium cyanate (NaCNO, 90 mg/kg; P50 decreased), o-iodosodium benzoate (OISB, 300 mg/kg; P50 increased), or sodium chloride (NaCl; P50 unchanged) to rats at a rate of 5 times/wk for 16 wk. At the end of this period, the animals were exposed to a low inspired O2 concentration and were subjected to exercise stress. Hill's n50 at pH 6.90–7.60, hematocrit, and the saturation dependency of the Bohr effect (PCO2 constant) were altered by NaCNO only. Cyanate-treated rats gained less weight, probably due to a toxic side effect of the drug. Hypoxemia-induced lactatemia was greatest with a high P50 (OISB). Physical effort (swimming) was tolerated poorly at normal arterial PO2 when P50 was low (NaCNO). Although a left-shifted curve appears beneficial when FIO2 is reduced, reasons for the physiological advantage may be the result of other characteristics of the O2 dissociation curve, not P50 alone.