ANGIOTENSIN-II BINDING-SITES IN THE RAT PANCREAS AND THEIR MODULATIONAFTER SODIUM LOADING AND DEPLETION

Specific I-125 angiotensin II binding sites were identified in the rat pancreas by radioreceptor assay, autoradiography and immunohistochemi stry. Scatchard analysis of the binding in normal rats yielded a K-d o f 0.51 +/- 0.23 nM with a B-max of 15 +/- 3.5 fmol/mg protein (means /- SD, n = 6), Changed plasma sodium concentration resulted in modific ations in the binding affinity and capacity, Sodium loading depressed both K-d (0.36 +/- 0.1 nM) and B-max (6.4 +/- 0.1 fmol/mg protein), wh ile sodium depletion elevated both K-d (2.03 +/- 0.3 nM) and B-max (45 +/-3.5 fmol/mg protein) (means +/- SD, n = 6), Autoradiography using I-125 Ang II and immunohistochemistry of the binding sites saturated w ith unlabeled Ang II and incubated with Ab-IIe(5) Ang II, revealed loc alization of the binding sites on the islet cell membranes and in the exocrine pancreas.