We examined how much tuna protein was required to enhance the glomerular filtration rate (GFR) of healthy young subjects. We conducted a creatinine clearance (Ccr) test three times, involving starvation and acute loads of baked tuna (157g: 43g, 0.68±0.11g/kg of protein; and 313g: 86g, 1.35±0.22g/kg of protein) with an interval of one week between each, on six healthy young subjects. Ccr during 1-2 hours after the acute 313g load of baked tuna was significantly enhanced (
p<0.05) compared with that of starvation. However, Ccr during the same period after the acute 157g load of baked tuna was not similarly enhanced. This result does not agree with that of Nakamura
et al., in which an acute 0.7g/kg load of tuna protein enhanced GFR in healthy subjects. This discrepancy might have arisen from the different subjects, experimental conditions and method of GFR measurement between the present authors and Nakamura
et al. A further study should be undertaken to examine the relationship between baked tuna protein loading and Ccr. Our result agrees with those reported by Hostteter and Rodriguez-Iturbe that an acute load of over 1.0g/kg of beefsteak protein enhanced Ccr, while 0.6g/kg did not. An amino acid analysis of the baked tuna protein was done and compared to that of beefsteak done previously. Almost the same amounts of glycine and arginine, which had been experimentally observed to enhance GFR, were contained in baked tuna and beefsteak. Further studies will determine the food material protein and amount required to enhance GFR in healthy subjects and the amino acid responsible.
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