1. We have observed that the alkaline Bohr effect of washed human fetal erythrocytes was larger than in human adult intact red cells, in physiological conditions of pH, PCO2 and temperature. This was also observed independently of the presence of CO2 and of 2,3 diphosphoglycerate (fresh or stored erythrocytes). 2. Experiments performed in purified HbFII and HbA1 solutions and direct titration of protons released upon oxygenation confirmed the larger alkaline Bohr effect of fetal hemoglobin, at physiological ionic strength. 3. At low chloride concentration HbFII solutions had an alkaline Bohr effect identical to that measured in HbA1 solutions. 4. Titration of purified Hb solutions with increasing concentrations of NaCl evidenced a lower O2 linked chloride binding by HbFII and predominantly at acid pH. 5. It is concluded that the larger alkaline Bohr effect of fetal erythrocytes of HbFII solutions is related to a diminished acid Bohr effect, due to the lower affinity of HbFII for chloride anions. 6. The physiological interest of these results for placental O2 transfer (double Bohr effect) and O2 delivery to the foetus is discussed.
The binding of various alkanes by proteins was recognized years ago. We have studied the effect of butene (C4Hx), a short-chain aliphatic hydrocarbon, on the functional properties of human adult hemoglobin. Under 1 atm pressure (100 kPa) butene decreased the affinity of hemoglobin (Hb) for oxygen (pso) by 45 % without altering the cooperativity of ligand binding. This effect was independent of pH (from 7.0 to 8.0) and of ionic strength. The changes in the affinity ofhemoglobin for oxygen were dependent upon the partial pressure of butene and evoked a saturating mechanism of the binding site(s). Mathematical simulation of the curve relating pso to the concentration of dissolved butene allowed us to calculate the apparent association constants for one single binding site KHb = 10.4 mmo1-l and KHboz = 1.53 mmol-' to Hb and Hb02 respectively. The larger binding of butene by Hb was confirmed by a 25 decrease in K1, the first association constant of oxygen to the tetrameric hemoglobin. It is concluded that butene is an allosteric effector of human Hb which acts most likely through hydrophobic interactions. It is postulated that the oxygen-linked binding site may be located at the c(1pz interface.
The pharmacokinetics and pharmacodynamics of vecuronium were studied in nine surgical patients with cholestasis, and in 14 patients without hepatic or renal disease. After the administration of vecuronium 0.2 mg kg-1 the plasma concentration of vecuronium and the degree of neuromuscular blockade were measured. The plasma clearance of vecuronium was decreased significantly (P less than 0.01) from 4.30 +/- 1.56 ml min-1 kg-1 (mean +/- SD) in normal patients to 2.36 +/- 0.80 ml min-1 kg-1 in patients with cholestasis. The elimination half-life was of 58 +/- 22 min in normal patients and was prolonged to 98 +/- 57 min (P less than 0.05) in patients with cholestasis. The total apparent volume of distribution was unchanged in patients with cholestasis. A prolonged neuromuscular blockade induced by vecuronium was observed in patients with cholestasis: the duration of effect from injection to 75% recovery of the twitch height was prolonged from 74 +/- 19 min in normal patients to 111 +/- 13 min in patients with cholestasis. The plasma concentration corresponding to 50% recovery from paralysis did not differ significantly between the two groups. Vecuronium has a prolonged effect in patients with cholestasis which is caused by a delay in its elimination.
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