STUDIES OF SUBCELLULAR CONTROL FACTORS IN HEARTS OF UREMIC RATS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 88  (4) , 563-570
Abstract
Subcellular fractions in hearts from rats with severe acute uremia (24 h after total nephrectomy) and moderate chronic uremia (2 wk after 5/6 nephrectomy) were studied and compared with preparations from acute and chronic sham-operated rats, respectively. Ca and Mg-sensitive actomyosin ATPase activities were normal in both groups. Acute uremia was associated with a significant depression of sarcolemmal Na+,K+ ATPase activity. Ca transport by fragmented sarcoplasmic reticulum was also depressed in the presence and absence of oxalate in acute uremia. Mitochondrial Ca transport and ATP and creatine phosphate (CP) concentrations were normal in these animals. Chronic uremic animals showed no abnormal subcellular mechanisms. A direct effect of acute uremia on some membrane functions in myocardial cells probably exists. The discrepancies observed between acute and chronic uremic groups may be due to a different degree of uremic state. The observation of depressed Ca transport by fragmented sarcoplasmic reticulum (FSR) in acute uremic hearts which were previously shown to have increased contractile reserve suggests that studies of Ca transport in FSR may not always truly reflect the contractile capacity of the heart.

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