Two unidentified arsenic metabolites were detected in the liver of rats on a gel filtration column by HPLC inductively coupled argon plasma mass spectrometry after an injection of dimethylarsinic (DMA(V)), dimethylarsinous (DMA(III)), monomethylarsonic (MMA(V)), or monomethylarsonous (MMA(III)) acid. The same arsenicals were also produced in vitro by incubation of DMA(III) in the liver supernatant but not by DMA(V). The two arsenic metabolites eluted at the same retention times as those of the two arsenicals prepared by reaction of DMA(V) with either thiosulfate plus disulfite or hydrogen sulfide or sodium sulfide plus sulfuric acid. The faster and slower eluting products on a gel filtration column were assigned as dimethyldithioarsinic acid (dimethylarsinodithioic acid) (DMTA(V)) and dimethylthioarsinous acid (DMTA(III)) from mass spectrometric data at m/z = 170 and 138 by electrospray ionization mass spectrometry with negative and positive ion modes, respectively. They were prepared selectively by reacting DMA(V) with hydrogen sulfide or sodium sulfide plus sulfuric acid under different reaction conditions. DMA(III) but not DMA(V) was transformed to DMTA(III) and DMTA(V) in the presence of sodium sulfide in vitro, suggesting that DMA(V) is reduced to DMA(III) with hydrogen sulfide, thiolated to DMTA(III), and then further thiolated oxidatively to DMTA(V). Metabolically, it is assumed that DMA(III) is transformed to DMTA(III) in the presence of sulfide ions, and then, DMTA(III) is oxidatively thiolated to DMTA(V). As the chemical species produced by reduction with the Reay and Asher method are DMTA(III) and DMTA(V), and different from DMA(III), the studies carried out with DMA(III) with the Reay and Asher method have to be reexamined.

We tested the hypothesis that induction of cyclo-oxygenase (COX) 2 mediates some effects of bone morphogenetic protein (BMP) 2 on bone. BMP-2 induced COX-2 mRNA and prostaglandin (PG) production in cultured osteoblasts. BMP-2 increased luciferase activity in calvarial osteoblasts from mice transgenic for a COX-2 promoter-luciferase reporter construct (

The natriuretic peptide family consists of three structurally related endogenous ligands: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and Ctype natriuretic peptide (CNP). The biological actions of natriuretic peptides are thought to be mediated through the activation of two guanylyl cyclase (GC)-coupled receptor subtypes (GC-A and GC-B). In this study, we examined the effects of ANP and CNP, which are endogenous ligands for GC-A and GC-B, respectively, on bone growth using an organ culture of fetal mouse tibias, an in vitro model of endochondral ossification. CNP increased the cGMP production much more potently than ANP, thereby resulting in an increase in the total longitudinal bone length. Histological examination revealed an increase in the height of the proliferative and hypertrophic chondrocyte zones in fetal mouse tibias treated with CNP. The natriuretic peptide stimulation of bone growth, which was mimicked by 8-bromo-cGMP, was inhibited by HS-142-1, a non-peptide GC-coupled natriuretic peptide receptor antagonist. The spontaneous increase in the total longitudinal bone growth and cGMP production was also inhibited significantly by HS-142-1. CNP mRNA was expressed abundantly in fetal mouse tibias, where no significant amounts of ANP and BNP mRNAs were detected. A considerable amount of GC-B mRNA was present in fetal mouse tibias. This study suggests the physiologic significance of the CNP/GC-B pathway in the process of endochondral ossification.Endochondral ossification requires the sequential formation and degradation of cartilaginous structures that serve as molds for the developing bones (1). Longitudinal bone growth is determined by the process of endochondral ossification in the cartilaginous growth plate, which is located at both ends of vertebrae and long bones (2). The control mechanisms that allow for coordinated bone growth throughout the body are poorly understood, but probably involve many systemic hormones and local regulators.Natriuretic peptides organize a family of three structurally related peptides: atrial natriuretic peptide (ANP), 1 brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) (3). ANP and BNP act as cardiac hormones that are produced predominantly by the atrium and ventricle, respectively (4 -8). CNP occurs in a wide variety of tissues (9 -12), where it acts as a neuropeptide as well as a local regulator. The biological actions of natriuretic peptides are thought to be mediated by intracellular accumulation of cGMP through the activation of particulate guanylyl cyclases (13). Two subtypes of guanylyl cyclase (GC)-coupled natriuretic peptide receptors (GC-A and GC-B) have been cloned so far (13). The rank order of ligand selectivity for GC-A and GC-B is ANP Ն BNP Ͼ Ͼ CNP and CNP Ͼ ANP Ն BNP, respectively (14, 15). Thus, ANP and BNP are thought to be endogenous ligands for GC-A, whereas CNP is selective for GC-B. A third natriuretic peptide receptor has been implicated in the metabolic clearance of ligands and thereafter named the clearanc...