Effect of Propranolol on Oxygen Binding to Hemoglobin In Vitro and In Vivo

Abstract

SUMMARYWe have shown that propranolol reduces oxygen binding by hemoglobin in intact red cells by increasing the selective permeability of the red cell membrane resulting in an exodus of potassium, chloride, and water. The latter effects result in a new distribution of hydrogen ion between cell and plasma, and thereby a reduction in red cell pH. The reduction in pH can fully explain the change in hemoglobin's affinity for oxygen based on the Bohr effect. Either D-or DL-propranolol can produce the change in red cell pH and oxygen binding by hemoglobin. The drug action on permeability is not prevented by epinephrine, although it is by chlorbutanol. Hence, the membrane action of propranolol does not appear to be related to its activity as a beta-adrenergic receptor blocking agent.Propranolol produced a marked alteration in red cell shape as well as in hydration (hypovolumic stomatocytes). The two effects were separable since dehydration of the cell by the addition of sucrose to plasma did not result in stomatocytes and chlorbutanol blocked the enhancement of permeability of the red cell membrane by propranolol without preventing the shape change (isovolumic stomatocytes). This suggests that propranolol may have two separate sites of membrane interaction.Propranolol (10 to 360 mg) administered to human subjects did not affect hemoglobin-oxygen affinity. This is explained by the fact that the concentration in blood after such doses is nearly 4,000 to 100-fold lower than that required to achieve changes in blood in vitro. Additional Indexing Words:Erythrocyte Hemoglobin-oxygen dissociation Cations THE DISCOVERY of the effect of red cell 2,3-DPG on hemoglobin-oxygen affinity1 led to the recognition that modulation of affinity by pharmacologic means might be useful. In an attempt to identify agents which might improve oxygen release by hemoglobin, scientists at Smith, Kline 4 We have examined further the effects of propranolol on human red cells in vitro and in vivo in order to 1) explore the mechanism by which affinity is altered in vitro, 2) re-examine the relationship of the propranolol effect to its f3-adrenergic blocking activity, and 3) re-examine the effect on affinity when the drug is administered to human subjects. Methods Preparation of BloodBlood was collected from the antecubital vein of healthy subjects and anticoagulated with sodium heparin. One-fifth volume of a solution of propranolol, epinephrine, or chlorbutanol dissolved in 0.15 M NaCl solution was added to blood to achieve the final concentration required by individual experiments. Blood in 10 ml tubes was centrifuged at 5,650 X g for 15 min in inverted position (stopper down). The packed red cells were aspirated into a syringe from which samples were expressed into both microhematocrit tubes and volumetric micropipettes. This technique allowed measurements to be made without washing treated cells. The red cells were packed to a volume of 97 to 98.5%. The P02 at which hemoglobin was 50% saturated at 370C, pH 7.4, pCO2 = 40 torr (P,0 std) was deri...

Oxyhaemoglobin equilibrium and chronic beta‐adrenoceptor blockade in coronary heart disease.

“…The effect of propranol on ion-fluxes across the erythrocyte membrane is not blocked by adrenaline (Lichtman et al, 1974). The view, that f3-adrenoceptors are not involved in this specific membrane action of propranolol is further supported by the fact, that the (+)-isomer of the drug, lacking ,3-adrenoceptor blocking properties, influences red cell volume and ion-permeability to a higher degree than the racemic (+)-propranolol (Pendleton et al, 1972;Lichtman et al, 1974). Alprenolol, in unphysiologically high doses, shares a 'local anaesthetic' property with propranolol and might theoretically influence haemoglobin oxygen affinity by a pharmacological action unrelated to /3-adrenergic receptor blockade.…”

“…From in vitro (Pendleton et al, 1972;Agostoni et al, 1973;Lichtman et al, 1974) and in vivo studies (Oski et al, 1972;Schrumpf et al, 1977) in humans there is evidence that propranolol might decrease haemoglobin oxygen affinity, a finding of obvious clinical relevance. To explain this effect essentially two theories were offered: (1) Propranolol might increase the concentration of unbound 2,3-DPG in erythrocytes (Oski et al, 1972).…”

“…In two in vivo studies demonstrating an effect of propranolol on P50 the carbonmonoxide haemoglobin binding was not investigated (Oski et al, 1972;Schrumpf et al, 1977). In addition, some negative in vivo studies have been published (Lichtman et al, 1974;Frishman et al, 1976;Brain et al, 1974;Bemtorp et al, 1979). The effect of propranol on ion-fluxes across the erythrocyte membrane is not blocked by adrenaline (Lichtman et al, 1974).…”

“…In addition, some negative in vivo studies have been published (Lichtman et al, 1974;Frishman et al, 1976;Brain et al, 1974;Bemtorp et al, 1979). The effect of propranol on ion-fluxes across the erythrocyte membrane is not blocked by adrenaline (Lichtman et al, 1974). The view, that f3-adrenoceptors are not involved in this specific membrane action of propranolol is further supported by the fact, that the (+)-isomer of the drug, lacking ,3-adrenoceptor blocking properties, influences red cell volume and ion-permeability to a higher degree than the racemic (+)-propranolol (Pendleton et al, 1972;Lichtman et al, 1974).…”

“…To a minor degree oxygen delivery may also be beneficially influenced by 83-adrenergic receptor blockade: Firstly, experimental data suggest that following,l8-adrenoceptor blockade myocardial blood flow is appropriately redistributed in favour of the subendocardium (Warltier et al, 1976). Secondly, in human studies propranolol has been reported to enhance tissue oxygenation by reducing the haemoglobin affinity for oxygen as reflected by a rightward shift of the oxyhaemoglobin equilibrium curve (Oski et al, 1972;Pendleton et al, 1972;Agostoni et al, 1973;Lichtman et al, 1974;Frishman et al, 1976;Schrumpf et al, 1977). However, conflicting data regarding this specific 33 pharmacological action of propranolol have been published (Brain et al, 1974;Berntorp et al, 1979).…”