Charcterization of atrial natriuretic peptide receptors (ANP-R) in rat kidney and lung tissues

The ability of several rat ANP analogues to compete with 125I-ANP(1-28) for binding to plasma membranes of rat kidney cortex (RKPM) and rat lung (RLPM) was examined. Their ability to compete on RKPM was: ANP(1-28)>pro-ANP>ANP(5-28)>ANP(5-27), ANP(5-25) being inactive. Conversely, the potency of the analogues on RLPM was: ANP(5-28)>ANP(5-27)>ANP(1-28)>ANP-(5-25), pro-ANP being unable to compete. The stimulation of particulate guanylate cyclase by these peptides paralleled their ability to compete. Truncation of the C-terminal therefore decreases the binding of the peptide to RKPM. In contrast, the N-terminal seems to be important for interaction with ANP-R on RLPM. ANP-R were photolabeled with 125I-iodo-azidosalicylyl-ANP(1-28) (ASA-ANP) or azidobenzoyl-125I-ANP(1-28) (AB-ANP) in which the C-terminal tyrosine is iodinated. In ASA-ANP, the iodine is located on the benzene ring. ASA-ANP identified a protein of ∼140 kDa in RKPM. AB-ANP recognized an additional protein of ∼120 kDa. The bulkier N-terminal of the ASA-ANP seems to hinder the binding of the analogue to the ∼120-kDa protein. In RLPM only the ∼120-kDa protein was detected by AB-ANP. The ∼140-kDa receptor may be unique to the kidney. ANF-R in RKPM and RLPM respectively, appear to interact with different domains of ANP suggesting the existence of two forms of the ANP-R