EXPRESSION OF RECEPTORS FOR ATRIAL-NATRIURETIC-PEPTIDE ON THE MURINE BONE MARROW-DERIVED STROMAL CELLS

Atrial natriuretic peptide (ANP) receptors were identified on both murine bone marrow-derived stromal cell lines A-3 and ALC and primary cultured cells using [I-125]ANP binding assays and Northern blot analyses. The binding of [I-125] ANP to the stromal cells was rapid, saturable, and of high affinity. The dissociation constants between ANP and its receptors on these cells showed no difference among cell types, while maximal binding capacity values were different among cell types. Competitive inhibition of [I-125]ANP binding with C-atrial natriuretic factor, specific for ANP clearance receptor (ANPR-C), revealed that most of [I-125]ANP-binding sites corresponded to ANPR-C. Northern blotting data corroborated that bone marrow-derived stromal cells expressed ANPR-C. However, in ALC cells, ANP biological receptors (either ANPR-A or ANPR-B), the mol wt of which is approximately 130K, were detected, and cGMP was accumulated after stimulation with ANP. On the other hand, in another stromal cell clone, A-3 cells, the expression of biological receptor was not detected in the affinity cross-linking and competitive inhibition experiments using [I-125]ANP. However, A-3 cells accumulated cGMP by responding to ANPR-B-specific ligand, C-type natriuretic peptide. These results suggest that ALC cells equally express ANPR-A and ANPR-B, while A-3 cells express ANPR-B dominantly. Although the physiological roles of these receptors in the bone marrow is still not resolved, ANP is expected to play a role in the regulation of stromal cell functions in bone marrow.