Uremic peak 2a in high performance liquid chromatography analysis of uremic plasma has already been reported in relation to uremic symptom and progression of renal failure. Inorder to study mechanism of production and excretion of peak 2a, 2a levels in plasma and in urine were compared with those of creatinine (Cr) and guanidino compounds in patients undergoing conservative therapy and hemodialysis, in this paper. With progression of renal failure, 2a levels increased exponentially in plasma, but did not much change in urine. This pattern resembled with that of guanidine, but different from those of Cr, guanidinosuccinic acid (GSA), methyl guanidine (MG) and guanidinoacetic acid (GAA), i. e., Cr, increase in plasma, decrease in urine; GSA and MG, increase both in plasma and urine ; GAA, small change in plasma, decrease in urine. Production of 2a was suggested to increase in renal failure, however its main production organ did not seem to be kidney. Ratio of clearance of 2a to Cr was found to be larger than unity in initial stage of renal failure, indicating existence of tubular excretion of 2a. The ratio rapidly decreased with progression of renal failure. Similar tendency was observed in GSA and GAA, however their clearance ratios to Cr were not correlated with that of 2a, therefore excretion mechanism was thought to be different between 2a and GSA.
