MORPHOMETRIC OBSERVATIONS ON THE EFFECTS OF ISCHEMIA IN THE ISOLATED PERFUSED RAT-HEART

The design of the experiment was to observe the changes which took place in the isolated perfused rat heart, that was made ischemic according to the technique of Neely et al. [16], using quantitative stereological techniques. The results showed that 24 min after myocardial failure there was a significant decrease in the fractional volume of myofibrils, mitochondria, T-system, and sarcoplasmic reticulum. The decrease in fractional volume of subcellular organelles can most probably be explained by myocardial cell swelling secondary to intercellular edema. There was also a decrease in the sarcoplasmic reticulum membrane area, and quantitative measurements indicated that this compartment was dilated. Observations on the intercalated disc indicated that there was a migration of acid phosphatase positive multivesicular bodies toward the disc interspace in ischemic hearts. This was found to be associated with the dissolution of gap junctions. Stereological measurements indicated that in ischemic hearts there was a 5-fold increase in the percentage of membrane area of the disc made up of open gap junctions, and that the number of vesicles from multivesicular bodies observed per μm3 of disc interspace was also proportionately higher. It is suggested that the multivesicular bodies represent elements of the lysosomal system and are responsible for the dissociation of the intercalated disc in ischemic hearts. © 1979.