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Atrial natriuretic peptide receptors on the corneal endothelium
R J Walkenbach1, G S Ye, M S Korenfeld
1Missouri Lions Eye Research Foundation, Columbia, MO 65201.
Purpose:
To ascertain whether the corneal endothelium exhibits specific receptors for atrial natriuretic peptide (ANP) and to characterize partially any binding activity.
Methods:
Most experiments employed radioligand-binding techniques to characterize 125I-ANP binding activity. Guanylate cyclase and corneal deturgescence assays were used in an attempt to correlate 125I-ANP binding activity with physiologic processes.
Results:
Corneal endothelial cells reversibly bound 125I-ANP with high affinity and exhibited a finite number of 125I-ANP binding sites. These binding sites also bound several ANP fragments but did not show binding affinity for the peptide hormone, vasopressin. Autoradiograms of affinity labeled ANP receptors separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed specifically radiolabeled proteins of several molecular weights in nonreduced samples, but only one major radiolabeled protein of 65 kd when samples were chemically reduced before separation.
Conclusions:
Corneal endothelial cells from several species exhibit specific binding of 125I-ANP. The binding characteristics of these receptors are similar to physiologic ANP receptors identified in other tissues. Several lines of evidence indicate that corneal endothelial ANP receptors are the "clearance" (ANP-C) type.