EFFECT OF CYCLIC-GMP PRODUCED BY NATRIURETIC PEPTIDES ON OSTEOBLAST-LIKE MC3T3-E1 CELLS

The C-type natriuretic peptide (10(-7) M) and atrial natriuretic pepti de (10(-7) M) enhanced cGMP accumulation by 418 and 83 times the contr ol value, respectively, in osteoblastlike MC3 T3-E1 cells. The natriur etic peptide B receptor was assumed to be the major natriuretic peptid e receptor. 8-Bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) ac tivated alkaline phosphatase doubled the activity versus the control v alue on day 15. Phosphodiesterase actvity was not stimulated by the ad dition of cGMP (1 mu M). cGMP-dependent protein kinase (G kinase) acti vity of the supernatant fraction was 25.5 pmol/min/mg protein. The 42 kDa protein band was detected to be phosphorylated by G kinase on SDS- PAGE. These results supported the hypothesis that natriuretic peptides regulate the differentiation of MC3T3-E1 cells through a cGMP-depende nt pathway.