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RESEARCH PRODUCT

Oxygen-haemoglobin dissociation curve in hypoxic rats of first or second generation.

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SUMMARY 1. Albino Wistar rats were raised in a normobaric hypoxic environment (10% O2 in N2). Two generations of hypoxic rats were observed for changes in their haemoglobin-oxygen (Hb-O2) dissociation curves (ODC), 2,3-diphosphoglycerate (2,3-DPG), haemoglobin (Hb), and Hill coefficients at P50 (n50). The first generation were called (H1) and the second generation (H2). The control group (N) had a normoxic environment. 2. Thirty-five rats (13 N rats, 12 H1 rats and 10 H2 rats) were used. The 2,3-DPG was significantly higher in both hypoxic groups when compared with N rats (2.02 ± 0.51 mmol/L) but 2,3-DPG of H2 rats was significantly lower than that of H1 rats (H1 = 3.48±0.58 mmol/L and H2 = 2.76±0.54 mmol/L). The haemoglobin values were N = 2.00±0.26, H1 = 2.65±0.32and H2 = 2.36±0.30 mmol/L, respectively. 3. We observed considerable differences in Hb-O2 affinity between the three groups of rats. In standard conditions (pH = 7.400; pCO2= 40 mmHg at 37°C) the H1 rats showed a significantly decreased Hb-O2 affinity (P50, st= 37.0 ± 1.3 mmHg) when compared with both H2 and N rats; the H2 rats showed a significantly increased Hb-02 affinity (P50, st 1 31.1 ± 1.5 mmHg) when compared with controls N (P50, st= 34.7±2.1 mmHg). There were no significant differences in n50 values: N = 2.88 ± 0.44; H1 = 2.88 ± 0.77; and H2 = 2.94 ± 0.67. 4. Therefore, the H1 rats’ ODC was located well to the right of that of N rats; and the H2 rats had an ODC located to the left when compared with both HI and N rats. It is likely that in H2 rats the adaptive processes to the new environment are more advanced; therefore, the magnitude of the compensatory mechanisms required to maintain a sufficient tissue oxygenation may be reduced.