AJP - Heart and Circulatory Physiology, Vol 247, Issue 3 380-H386, Copyright © 1984 by American Physiological Society
Total adenine nucleotide stores and sarcoplasmic reticular Ca transport in ischemic rat heart
H. Meno, H. Kanaide, M. Okada and M. Nakamura
We studied the relation between the contractility and metabolic changes in
reperfusion after ischemia, and the effect of diltiazem on these changes,
in an isolated rat heart perfused using the Langendorff method. After
aerobic perfusion at 80 cmH2O, the perfusion pressure was reduced to 10
cmH2O to induce global ischemia. Substrate was removed from the perfusate
during ischemia. After 30 or 60 min of ischemia, the heart was reperfused
in an aerobic condition. During ischemia, the total adenine nucleotide
level (TAN: sum of ATP, ADP, and AMP) was progressively reduced and the
ATP-to-ADP ratio was one-third of the value obtained in an aerobic
condition. With 30 min of subsequent reperfusion, ATP increased, and the
shorter the duration of ischemia, the closer ATP/ADP approached the value
of an aerobic condition, whereas TAN was equivalent to the value shown
immediately before reperfusion. Thus the degree of ATP recovery by
reperfusion mainly depends on the amount of TAN immediately before
reperfusion and the mitochondrial function of oxidative phosphorylation
that determines ATP/ADP. The calcium transport activity of the sarcoplasmic
reticulum of myocardial cells was affected by ischemia and showed no
amelioration or further deterioration by subsequent reperfusion. When
diltiazem (10(-5)M) was added to the perfusate continuously from 5 min
before ischemia, during ischemia, and until 10 min of reperfusion, the
amount of TAN in ischemia and reperfusion and the calcium transport
activity during reperfusion were maintained at relatively high levels. The
degree of contractility recovery by reperfusion showed direct correlations
with both the tissue ATP amount and the level of calcium transport activity
in the sarcoplasmic reticulum.
