Synthesis of creatine in nephrectomized rats

¹ Veterans Administration Hospitals, Sepulveda and Los Angeles, and Department of Medicine, University of California Medical Center, Los Angeles, California

Glycocyamine, the creatine precursor, is reportedly synthesized in the kidney. Nephrectomized rats, kept alive by peritoneal dialysis for periods up to 17 days, showed a slight initial increase in total body and muscle creatine concentration, followed after 10 days by a slight decrease. The failure to observe the anticipated loss in creatine concentration after nephrectomy may be due to extrarenal glycocyamine synthesis, conservation of creatine released by catabolized tissue with loss in body weight, or reduced creatine breakdown. Nephrectomized rats were found to convert 6–20% as much C¹⁴-labeled glycine to creatine as unoperated controls. Ureter-ligated rats converted 35% of the control amount of glycine to creatine. Sham-operated rats produced essentially normal amounts of creatine. These data indicate that there is a nonrenal pathway of creatine synthesis which can produce 20% of the normal requirement. Other data suggest that 40–60% of creatine synthesis may be by extrarenal routes.

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