CHARACTERIZATION OF BINDING-SITES FOR AMYLIN, CALCITONIN, AND CGRP INPRIMATE KIDNEY

Analysis of receptor distributions for I-125-labeled amylin, I-125-lab eled calcitonin, and I-125-labeled calcitonin gene-related peptide (CG RP) in Macaca fascicularis kidney by in vitro autoradiography revealed distinct patterns of binding for each peptide. I-125-rat amylin bound primarily to the cortex, being associated with the distal tubule, inc luding apparent binding to the juxtaglomerular apparatus. I-125-salmon calcitonin displayed high-density binding in the cortex with low-dens ity binding to the medulla. Emulsion autoradiography indicated that bi nding was associated with both distal tubule and thick ascending limb of the loop of Henle. Intense binding was also found often over juxtag lomerular apparatus. I-125-rat CGRP-alpha exhibited low-to moderate-de nsity binding to the inner medulla/papilla with high-density binding o ver small-, medium-, and large-caliber arteries. Weak binding to the g lomerulus was also seen, but no binding was associated with cortical t ubules. Competition binding studies, performed with each of the radiol igands, revealed peptide specificity profiles for CGRP and calcitonin receptors that were similar to those described in rat. However, the mo nkey amylin receptors differed from those in rat, exhibiting relativel y higher affinity for calcitonin peptides but reduced affinity for CGR P peptides. These studies suggest potential roles for amylin, calciton in, and CGRP in primate renal function.