Prostaglandin [E.sub.2] activates outwardly rectifying [Cl.sup.-] channels via a cAMP-dependent pathway and reduces cell motility in rat osteoclasts

We examined changes in electrical and morphological properties of rat osteoclasts in response to prostaglandin (PG)[E.sub.2]. PG[E.sub.2] (> 10 nM) stimulated an outwardly rectifying [Cl.sup.-] current in a concentration-dependent manner and caused a long-lasting depolarization of cell membrane. This PG[E.sub.2]-induced [Cl.sup.-] current was reversibly inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), and tamoxifen. The anion permeability sequence of this current was [I.sup.-] > [Br.sup.-][approximately equal to] [Cl.sup.-] > [gluconate.sup.-]. When outwardly rectifying [Cl.sup.-] current was induced by hyposmotic extracellular solution, no further stimulatory effect of PG[E.sub.2] was seen. Forsknlin and dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) mimicked the effect of PG[E.sub.2]. The PG[E.sub.2]-induced [Cl.sup-] current was inhibited by pretreatment with guanosine 5'-O-2-(thiodiphosphate) (GDP[beta]S), Rp-adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS), N-(2-[p-bromocinnmnylamino]ethyl)-5-isoquinolinesulfonamide dihydrochloride (H-89), and protein kinase A inhibitors. Even in the absence of nonosteoclastic cells, PG[E.sub.2] (1 [micro]M) reduced cell surface area and suppressed motility of osteoclasts, and these effects were abolished by Rp-cAMPS or H-89. PG[E.sub.2] is known to exert its effects through four subtypes of PGE receptors (EP1-EP4). EP2 and EP4 agonists (ONO-AE1-259 and ONO-AE1-329, respectively), but not EP1 and EP3 agonists (ONO-DI-004 and ONO-AE-248, respectively), mimicked the electrical and morphological actions of PG[E.sub.2] on osteoclasts. Our results show that PG[E.sub.2] stimulates rat osteoclast [Cl.sup.-] current by activation of a cAMP-dependent pathway through EP2 and, to a lesser degree, EP4 receptors and reduces osteoclast motility. This effect is likely to reduce bone resorption. prostanoid receptor agonists; electrophysiology; motile activity; bone resorption