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2 Neurobiology Unit,
Analysis of receptor distributions for
125I-labeled amylin,
125I-labeled calcitonin, and
125I-labeled
calcitonin gene-related peptide (CGRP) in
Macaca
fascicularis kidney by in vitro
autoradiography revealed distinct patterns of binding for each peptide.
125I-rat amylin bound primarily to
the cortex, being associated with the distal tubule, including apparent
binding to the juxtaglomerular apparatus.
125I-salmon calcitonin displayed
high-density binding in the cortex with low-density binding to the
medulla. Emulsion autoradiography indicated that binding was associated
with both distal tubule and thick ascending limb of the loop of Henle.
Intense binding was also found often over juxtaglomerular apparatus.
125I-rat CGRP-
exhibited low-
to moderate-density binding to the inner medulla/papilla with
high-density binding over small-, medium-, and large-caliber arteries.
Weak binding to the glomerulus was also seen, but no binding was
associated with cortical tubules. Competition binding studies,
performed with each of the radioligands, revealed peptide specificity
profiles for CGRP and calcitonin receptors that were similar to those
described in rat. However, the monkey amylin receptors differed from
those in rat, exhibiting relatively higher affinity for calcitonin
peptides but reduced affinity for CGRP peptides. These studies suggest
potential roles for amylin, calcitonin, and CGRP in primate renal
function.
calcitonin gene-related peptide; autoradiography; G protein-coupled receptor
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