Interruption of Perfusion of Isolated Rabbit Heart upon Reaction of Coronary Flow.

Abstract

We have not found described the effect of interruption of the perfusion of the isolated mammalian heart upon the reaction of the coronary flow immediately subsequent to resumption. This very simple experiment may be used to demonstrate one of the most fundamental chemical properties of muscle, increased acid production under conditions of inadequate oxygen supply. This increased acidity is demonstrable with the isolated rabbit heart, perfused with Ringer-Locke solution. In some instances we have altered the formula, using CaCl2, 0.012% instead of 0.024%, or varying the NaHCO3 strength; the former change appears immaterial to the result, but reduction in NaHCO3 strength makes the reaction very distinct. In order that the perfusion fluid may wash the heart of blood and clear the tissue of accumulated diffusible acid products in unusual amount, perfusion is carried out for 20 or 30 minutes, when the beat has usually become fairly regular, and the fluid escaping from the heart nearly constant in reaction from minute to minute. The perfusion is then stopped by clamping off the tube leading from the Ringer reservoir, or by lowering of the perfusion pressure from the usual adequate value of 50 to 70 cm. of Ringer to about 4 cm. The latter procedure may readily be carried out with the apparatus used by us by providing a rubber tube connection of adequate length for the Ringer reservoir. With zero or inadequate perfusion pressure so caused, the heart not infrequently shows at first a period of increased force of beat, but soon becomes irregular and finally stops at the end of usually 8 to 20 minutes. If the perfusion is now resumed with the former pressure, the fluid escaping from the heart is more acid than before for a period of 1 to 5 minutes or even longer, and not infrequently also temporarily increased in amount.