Glomerular filtration rate (GFR; creatinine clearance) and renal excretion rates of active kallikrein, prokallikrein, and kinins were measured in seven normal male subjects after a week on a constant low (40 g/day)-protein diet (LP) and during a subsequent week when only protein content was increased to 140 g/day (HP). Renal kinin excretion increased from 19.7 +/- 1.2 micrograms/day on day 7 of LP to 26.0 +/- 2.5 on day 1 of HP (P less than 0.002), and this higher rate persisted during HP. Active kallikrein excretion increased from 105 +/- 16 to 171 +/- 40 micrograms/day on day 2 of HP (P less than 0.006). Prokallikrein excretion did not increase significantly until day 4 of HP, 52 +/- 16 vs. 96 +/- 38 micrograms/day (P less than 0.03). The increases in active kallikrein and kinin excretion preceded an increase in GFR, which went from 117 +/- 6.8 ml/min on LP to 130 +/- 10 ml/min on day 5 of HP (P less than 0.003). At the end of the LP diet, acute ingestion of 40 g of a casein solution produced an increase in kinin excretion after 2 h (586 +/- 64 vs. 402 +/- 33 pg/min, P less than 0.001) and further to 640 +/- 74 pg/min at 3 h (P less than 0.001). This was accompanied by an increase in GFR at 3 h (154 +/- 18 vs. 132 +/- 10 ml/min, P less than 0.05). Kinin excretion rate correlated directly with GFR during both chronic (r = 0.87) and acute (r = 0.77) studies.(ABSTRACT TRUNCATED AT 250 WORDS)