Localization of 125I-labelled alpha-r-atrial natriuretic peptide in rat tissues by whole-body and microautoradiography.

125I-labelled alpha rat atrial natriuretic peptide (28 amino acids: Ser 99-Tyr 126) ([125I]alpha-rANP) was given i.v. to Sprague-Dawley rats and the distribution of radioactivity in the tissues was examined by whole-body and microautoradiography at intervals from 2 min to 4 h after the administration. Inhibition of uptake of the [125I]alpha-rANP by simultaneous injection of an excess of non-labelled alpha-rANP was taken as an indication that highly labelled structures in rats injected with [125I]alpha-rANP alone are due to an abundance of specific receptors for the peptide. In the rats given only the [125I]alpha-rANP a rapid and high radioactivity occurred in the renal glomeruli, the endocardium of the heart ventricles, the endothelium of the processus ciliares of the eyes, the portal vessels and a few larger vessels of the liver, the subcapsular vessels of the adrenal glands and the parenchyma of the lungs. Other tissues showing a distinct, but less prominent, radioactivity were the endocardium of the heart atria, the walls of the great afferent and efferent vessels in the thoracic cavity, the choroid plexuses of the brain ventricles, the pia mater, brown fat, the muscularis layer of the stomach and the intestines, the lamina propria of the villi in the small intestine and the walls of a few small blood vessels in the kidney medulla. The specific labelling was highest at 2 min after injection and then diminished at later intervals.(ABSTRACT TRUNCATED AT 250 WORDS)