THE CLEARANCE OF CREATINE IN DOG AND MAN

Abstract

[Exp. showed that] the clearance of creatine in the dog is a curvilinear function of plasma conc. At low plasma conc. the creatine clearance (CC) approaches zero, i.e., the urine is essentially creatine-free, but as the plasma conc. is raised the CC rises sharply. At plasma conc. of 15-120 mgm.% the CC in the dog is intermediate between the simultaneously determined xylose (or sucrose) and creatinine clearances, averaging 20% above the former and 13% below the latter. Between 6 and 40 mgm.% of plasma creatine, the CC in man is equal to the xylose clearance (the av. is identical) while the creatinine clearance averages 49% higher [5 exps. on 1 ([male] and 1 [female] subject]. No apparent differences were found between the sexes in the mechanism of creatine excretion at the plasma levels of creatine investigated. The excretion of creatine (either in terms of absolute CC or relative to xylose) is unaffected by the intraven. administration of neutral Na phosphate. The intraven. administration of glycin, which increases all renal clearances, raises the xylose clearance relatively more than the CC.