Isolation of cyclo(His-Pro)-like immunoreactivity from human urine and demonstration of its immunologic, pharmacologic, and physico-chemical identity with the synthetic peptide.

Measurements of cyclo(His-Pro) levels in human urine were carried out by specific radioimmunoassay. Cyclo(His-Pro)-like immunoreactivity in Human urine was found to be immunologically, pharmacologically, and physico-chemically identical to that of synthetic cyclo(His-Pro). The concentration of urinary cyclo(His-Pro) in 24-h collection was 1133.8 +/- 122.5 nmol/L, with a range of 606 to 1865 nmol/L. The daily excretion rate of cyclo(His-Pro) was 1812 +/- 248 nmol cyclo(His-Pro)/g creatinine, or 1814 +/- 199 nmol cyclo(His-Pro/day.