Effects of chronic changes in hemoglobin-O2 affinity in rats

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Abstract
The characteristics of O2 transport following chronic i.p. administration of sodium cyanate (NaCNO, 90 mg/kg; P50 [O2 partial pressure at half Hb saturation] decreased), o-iodosodium benzoate (OISB, 300 mg/kg; P50 increased) or NaCl (P50 unchanged) to rats at a rate of 5 times/wk for 16 wk were assessed. 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 [CO2 partial pressure] constant) were altered at 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 [O2 partial pressure] 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.