Standard and pH-affected hemoglobin-O 2 binding curves of Sprague-Dawley rats under normal and shifted P50 conditions

Abstract

1. 1. The oxygen saturation ( SO 2) was determined of Sprague-Dawley rat blood having increased hemoglobin (Hb)-O 2 affinity ( P 50 < 37mmHg) or capacity ( C max) over a range of pH's. 2. 2. Rats were untreated (K), or had passed 14 d drinking 0.5% saline (C; ctrl) or NaOCN (N; chronically low P 50 high C max), 5000m altitude acclimatization (H; high C max), or exchange transfusion with OCN −-Hb red cell blood (X; acutely low P 50). 3. 3. The P 50 [mmHg], Hill's “ n”, and C max [ml O 2/100 ml], measured after tonometry, were 36.0, 2.60 and 20.6 (K), 32.6, 2.50 and 21.8 (C), 18.3, 2.35 and 23.9 (N), 36.0, 2.60 and 29.4 (H), and 24.9, 2.73 and 22.3 (X). 4. 4. Oxygen dissociation curves (ODC's), derived from simultaneous SO 2 and PO 2 measurements during deoxygenation ( PO 2: 100-0 mmHg) of blood (normal and acidified with CO 2 or lactic acid), delivered Bohr coefficients (BC CO 2 , BC Lac) each differing between groups (C vs N) above SO 2 50%; within groups BC CO 2 vs BC Lac differed at SO 2 10–90% ( P < 0.05). 5. 5. Group-specific ODC's and pH-shifted curves (± 0.05, ± 0.10 and ±0.15 units from 7.4, relying on BC CO 2 ) are plotted for direct reading of SO 2 and, with C max, accurate data on blood O 2 content are obtained; corrections for lactic acidosis are discussed.