A comparison of the renal actions of gamma-L-glutamyl-L-dopa and gamma-L-glutamyl-L-tyrosine in normal man

1. The renal responses to the dipeptides gamma-L-glutamyl-L-dopa (gludopa) and gamma-L-glutamyl-L-tyrosine (glutyrosine) were compared when given intravenously in six normal male volunteers. 2. Gludopa is natriuretic and diuretic at a dose of 25 micrograms min-1 kg-1. At the same dose, glutyrosine had no effect on the volume or sodium content of the urine. 3. There was a 400-600-fold increase in urine dopamine output after gludopa; there was no conversion of glutyrosine to dopamine. 4. Gludopa significantly inhibited plasma renin activity, whereas with glutyrosine there was a non-significant increase. 5. Gludopa is a potent pro-drug for renal dopamine production and exerts natriuretic and hormonal effects. Glutyrosine appears to be inactive. The results support the contention that circulating L-dopa is the important physiological precursor for renal dopamine.