INFLUENCE OF ALKALINE BUFFERS ON CYTOPLASMIC PH IN MYOCARDIAL-CELLS EXPOSED TO METABOLIC-ACIDOSIS

The influence of different clinically used alkaline buffers on cytopla smic pH in normal as well as acidotic rat myocardial cells was investi gated in this study by means of the fluorescent intracellular probe 2' ,7'-bis-(carboxyethyl)-5,6-carboxyfluorescein acetoxymethyl ester (BCE CF-AM). It was shown that both sodium bicarbonate and Tris buffer mixt ure (Tribonat(R)) caused a significant and dose-dependent acidificatio n of the cytoplasm of suspended myocardial cells with normal initial i ntracellular pH. This decrease was followed by a slow increase during the observation period. The initial cytoplasmic pH value was more easi ly reached when Tris buffer mixture was used. Ringer's acetate also ca used a decrease of intracellular pH, but this change persisted and was further amplified during the experiment. Carbicarb in larger dosages as well as pure trometamol (Tris) caused a pronounced dose-dependent a nd lasting intracellular alkalinization. Intracellular acidosis was ac hieved by preincubating the cells in sodium acetate. Addition of sodiu m bicarbonate caused an initial and dose-dependent acidification of th e cytoplasm followed by a slow increase to values slightly above the i nduced acidosis. In contrast, Tris buffer mixture showed a tendency to wards an initial acidification only when larger dosages were used, and correction of the induced acidosis was possible by use of moderate to large volumes. Ringer's acetate produced a lasting and dose-dependent decrease of cytoplasmic pH, while Carbicarb and pure trometamol cause d an immediate, pronounced and persistent alkalinization. Myocardial c ells with low initial cytoplasmic pH due to preincubation in an acid b uffer also showed an early decrease of intracellular pH after addition of sodium bicarbonate and Tris buffer mixture. In the case of sodium bicarbonate correction of the acid-base disturbance was not achieved d uring the observation period, while this was accomplished by use of la rger volumes of Tris buffer mixture. Carbicarb in larger volumes cause d an increase in intracellular pH. The most significant and persistent increases of cytoplasmic pH was achieved by use of pure trometamol. I n conclusion, the present in vitro study implies that Tris buffer mixt ure (Tribonat(R)) is well-suited for correction of intracellular acido sis since it acts without causing a pronounced initial intracellular a cidosis or a later potentially hazardous huge cytoplasmic alkalinizati on.