Localization, synthetic regulation, and biology of renal atriopeptin-like prohormone

We recently demonstrated the synthesis and secretion of an atriopeptin (AP)-like prohormone in rat neonatal and adult cortical kidney cell cultures. However, these cultures contained proximal as well as distal tubular epithelial cells; thus characterization of the peptide synthetic cell was not possible. Also, by immunohistochemical techniques, we localized this AP-like prohormone to the distal cortical nephron in adult rat kidney. In this study, we examined further details of the kidney cortical cell type that expresses and secretes this AP-like peptide in adult renal cortical cell cultures, its regulation by adenylate cyclase via adenosine 3',5'-cyclic monophosphate (cAMP) generation, and its ability to stimulate guanylate cyclase. Tubular fragments were derived from cortical tissue of adult Sprague-Dawley rats and separated into four fractions on Percoll density gradient. Cell cultures generated from fraction 3 secreted 5- to 10-fold the amount of this renal peptide compared with fractions 2 and 4. Further cell culture characterization was performed by agonist-stimulated cAMP formation, kallikrein localization, and prostaglandin E2 formation. From these analyses, it was determined that tissue band 3 was enriched for distal cortical connecting tubules. To further evaluate whether mammalian distal nephron synthesizes an AP-like protein, we determined that two immortalized mouse cell lines, derived from either the distal convoluted tubule or cortical collecting tubule, synthesized a radiolabeled AP after being pulsed with [35S]-methionine.(ABSTRACT TRUNCATED AT 250 WORDS)