Binding of [3H]bradykinin in isolated nephron segments of the rabbit

Binding of intrinsically labeled [3H]bradykinin was studied in isolated nephron segments of the rabbit. Highest binding was observed in the cortical collecting tubule (5.76 +/- 0.34 X 10(-18) mol/mm) and the outer medullary collecting tubule (5.24 +/- 0.25 X 10(-18) mol/mm, means +/- SE, n = 6). Small but significant binding was also seen in the glomerulus, proximal straight tubule, cortical thick ascending limb of Henle's loop, and distal convoluted tubule. Lysyl-bradykinin, methionyl-lysyl-bradykinin, and tyrosine-8-bradykinin (but not des-arginine-9-bradykinin, vasopressin, angiotensins I and II, or prostaglandins) competed with [3H]bradykinin. The site of highest kinin binding (collecting tubule) is downstream from the highest concentration of kallikrein (granular portion of distal convoluted tubule). The binding data indicate that the major sites of kinin action in the kidney are the cortical and medullary collecting tubules. One action of kinins could be the stimulation of prostaglandin synthesis in the collecting tubules, which are known to actively synthesize prostaglandins.