MORPHOLOGICAL-CHANGES INDUCED BY PROSTAGLANDIN-E IN CULTURED RAT OSTEOBLASTS

Prostaglandin E (PGE)-induced morphological changes of osteoblasts and its possible mechanisms mere investigated in cultured calvaria and is olated osteoblasts from long bone fragments of neonatal rats. The cont rol osteoblasts, either on the calvaria or isolated from the long bone fragments, were flat, polygonal in shape, and arranged in a monolayer under scanning electron microscopy (SEM) or phase contrast microscopy . Treatment with 1 mu mol/L of prostaglandin E-2 (PGE(2), 2 h) caused these bone cells to contract a soma, whereas 10 and 100 mu mol/L PGE(2 ) (2 h) caused 18%-30% of the bone cells to elongate and expose the un dersurface. Incubation of the cultured osteoblasts with PGE, at differ ent time periods showed a bell-shaped pattern with the optimal respons e at 2 h of incubation. A similar reaction can be induced by treatment with prostaglandin E-1 (PGE(1)) or dibutyryl cyclic adenosine monopho sphate (DBcAMP) in combination with 3-isobutyl-1-methylxanthine (IBMX) . Furthermore, we assessed the percentage of responsive isolated bone cells to investigate interactions with other agents. The morphological changes induced by PGEs were inhibited by H-8, a protein kinase inhib itor. On the other hand, elevated intracellular calcium enhanced the P OE-induced morphological changes. Fluorescence labeling showed that PG Es caused the breakdown of the actin microfilaments, but spared the mi crotubules and vimentin filaments in the isolated osteoblast-like cell s, These results suggest that the morphological changes of osteoblasts induced by PGEs may be related to the intracellular cAMP and calcium levels, (C) 1998 by Elsevier Science Inc. All rights reserved.