[Observations of changes in ultrastructure and calcium ion distribution in rabbit heart after various periods of ischemia].

The ultrastructural degenerative changes and calcium ion distribution observed in the rabbit myocardium after various periods of ischemia and 30 minutes after postischemia reperfusion after 30 minutes reperfusion following 15 minutes of ischemia, near complete recovery of substructures is seen, anyhow the number of calcium ion deposits along the sarcolemma are still lower than normal. After 30 and 45 minutes of ischemia, severe degenerative changes in various cellular substructures took place. The sarcolemma of most myocytes became devoid of precipitate. After reperfusion, large calcium ion deposits accumulated in the form of clusters in the mitochondria. It was recognized that the herein described cytochemical calcium ion shifts may be indicative of structural damage bordering irreversibility. After 60 to 75 minutes of ischemia and then postischemia reperfusion, cell damage is observed as disrupted sarcolemma completely devoid of calcium ion deposit, large swollen mitochondria without signs of calcium ions and presence of flocculent precipitates, all signs of terminal impairment of metabolism.