C-type natriuretic peptide/guanylate cyclase B system in ATDC5 cells, a chondrogenic cell line

Natriuretic peptides constitute a family of three structurally related peptides: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). Particulate guanylate cyclases, GC-A, and GC-B, are the receptors for these peptides to mediate their action. ANP and BNP possess high affinities for GC-A, and CNP is the preferred ligand for GC-B. In this article, we report our study of the expression and possible role(s) of natriuretic peptides in ATDC5 cells, which represent a chondrogenic cell line. ATDC5 cells produced cyclic guanosine monophosphate (cGMP) in response to natriuretic peptides. CNP was far more potent than ANP in terms of cGMP production. The messages for GC-A and GC-B were demonstrated by means of Northern blot analysis, and the presence of CNP was shown by Southern blotting coupled with reverse transcription-polymerase chain reaction (RT-PCR). These results suggest that the CNP/GC-B system is preferentially expressed in ATDC5 cells. GC-B mRNA expression was higher at 14 days after confluency than that at confluency. CNP or 8-bromo cGMP reduced [³H] thymidine uptake and slightly increased the message for collagen type X, which is a marker of hypertrophic chondrocytes. These data suggest that the CNP/GC-B system is likely to be an autocrine/paracrine regulator of ATDC5 cells, thus affecting both their growth and differentiation.