Age-dependent renal responses to the bradykinin B(2)- receptor antagonist icatibant in conscious lambs.

To investigate the role of endogenously produced bradykinin in modulating renal function during postnatal maturation, various parameters of glomerular and tubular function were measured for 1 h before and after intravenous injection of 12.5 microg/kg of the specific B(2)-receptor antagonist icatibant to conscious, chronically instrumented lambs aged approximately 1 (n = 7) and approximately 6 wk (n = 7). In response to icatibant, and in the absence of any changes in renal hemodynamics, there was an approximately 80% decrease in glomerular filtration rate (GFR) at 20 min in 1-wk-old lambs that was sustained for 60 min; in 6-wk-old lambs, there was an approximately 70% decrease in GFR by 20 min, with control levels being reached by 40 min. Icatibant administration was also associated with significant decreases in urinary flow, Cl(-), and K(+) excretion rates that were similar in both groups of lambs, whereas Na(+) excretion decreased only in 6-wk-old lambs. We conclude that bradykinin modulates glomerular and tubular function in an age-dependent manner.