Catecholamine effect on HCO3-/Cl- exchange and rabbit myocardial cell pH regulation

The possible effect of isoproterenol on a HCO3-/Cl- exchange in mammalian myocardium and its role on intracellular pH (pHi) regulation was studied in isolated perfused rabbit hearts. pHi was determined from the distribution of 5.5-dimethyl-2,4-oxazolidinedione (DMO). Perfusates contained either 137.4 or 4.4 mM Cl-. In the latter case, Cl- was replaced by glucuronate. Hearts were perfused with low [Cl-] Ringer for 1 h in order to deplete the cell of Cl-. Isoproterenol (10(-5) M) was infused for the last 15 min of perfusion in approximately half of the preparations. Reduction of [Cl-], both in the untreated and in the isoproterenol-treated preparations resulted in an increase in pHi. Isoproterenol increased tissue cAMP concentration by approximately 2.5 fold both in hearts perfused with normal and with low [Cl-] Ringer. In the presence of normal [Cl-], isoproterenol had an alkalinizing effect when acid loads were introduced. This effect was abolished by the reduction of [Cl-]. These results support the idea that the catecholamine-cAMP system stimulates a HCO3-/Cl- exchange in mammalian myocardium.