The expression and secretion of atrial natriuretic factor and brain natriuretic peptide by rat proximal tubular cells

We examined the expression of both the natriuretic peptides and natriuretic peptide receptors (NPR) in primary cultures of rat proximal tubular (Rm) c ells using Northern blot assay fur peptides and receptors and radioimmunoas say and immunohistochemical analysis for atrial natriuretic factor (ANF), b rain natriuretic peptide (BNP), and C-type natriuretic peptide. Freshly iso lated cells expressed mRNA coding for ANF, BNP, and the NPR-C. The presence of ANF and BNP in freshly isolated cells was confirmed by immunocytochemic al staining. As cells approached confluence, there was a marked increase in mRNA expression for ANF and BNP. Immunocytochemical analysis and radioimmu noassay confirmed that both these peptides were co-localised in RPT cells a nd present in the cell supernatant. These changes in peptide expression wer e associated with a concurrent decrease in the expression of the NPR-C and the appearance of the NPR-A and -B. These results confirm that freshly isol ated RIFT cells possess the components of an autocrine natriuretic peptide system and that growth in primary culture is associated with changes in bot h peptide system and that growth in primary culture is associated with chan ges in both peptide and receptor subtype expression, raising the possibilit y that the endogenous production of ANF and BNP may be involved in the cont rol of control cell growth. BIOCHEM PHARMACOL 59;7:783-790, 2000. (C) 2000 Elsevier Science Inc.