ABSTRACT
A surgical preparation that allows chemical alteration of the blood supplied to specific area of the intact heart was used to investigate the effects of lowered tissue pH on the fine structure of myocardial cells. Controlled infusion of isotonic saline acidified with HCl to a pH value between 1.0 and 2.0 produced a lowering of blood pH to values of less than 7.0. This drop in the pH of the perfusing blood resulted in a corresponding decrease in pH of the relevant area of myocardium. When this decrease occurred without a concomitant increase in tissue lactate level, the myocardial cells of the acid-perfused area showed focal glycogen depletion, moderate relaxation of myofibrils and clumping of nuclear chromatin, and mild mitochondrial change, which did not include marked swelling although intramitochondrial electron-dense inclusions were often detectable. When the fall in pH was accompanied by a large increase in lactate concentration, however, the cells showed more severe glycogen depletion and clumping of nuclear chromatin, and mitochondrial change, which did include marked swelling, together with the presence of well developed inclusions.
Subject(s)
Myocardium/ultrastructure , Animals , Chromatin/ultrastructure , Cytoplasmic Granules/ultrastructure , Dogs , Female , Glycogen , Hydrogen-Ion Concentration , Lactates/metabolism , Male , Mitochondria, Muscle/ultrastructure , Myocardium/metabolism , Myofibrils/ultrastructureABSTRACT
The progressive changes in pH, lactate content, and light and electron microscopic appearances were studied in dog myocardium undergoing a 6-hour period of autolysis in vitro at 37 degrees C. and at room temperature. At 37 degrees C. there was a rapid cumulative fall in pH during the 1st hour after excision of the heart and a corresponding increase in lactate content, but little additional change in either subsequently. The nature and sequence of the morphologic alterations at this temperature were generally similar to those which occur in ischemic myocardium in vivo. At room temperature, a much slower cumulative decrease in pH and increase in lactate content took place throughout the whole period of investigation and was paralleled by a slower rate of development of morphologic change.
