The Effect of Misoprostol and Prostanoids On cAMP Production and Calcification in a Differentiating Chick Limb-Bud...

Mesenchymal cells isolated from chick limb-buds, when plated in micromass culture, differentiate into chondrocytes, forming a mineralizable matrix. Because these cells produce prostanoids during differentiation, this system was used to test the hypothesis that E-series prostanoids are involved in chondrocyte-mediated calcification. Prostaglandins E(2) (PGE(2)) and E(1) (PGE(1)), and the E-series analog, misoprostol (MP), increased chondrocyte cAMP content in the presence of the phosphodiesterase inhibitor IBMX. The increases for PGE(1) and PGE(2) at their saturation concentrations were twofold to threefold greater than for MP at its saturation concentration. At culture day 7, 9, or 11 (the day that mineralization commenced), the maximal cyclic adenosine monophosphate (cAMP) production was at a concentration of 250--500 ng/ml PGE(2), 500--1000 ng/ml PGE(1), and less-than-or-equal5000 ng/ml MP. At these concentrations, PGE(1) and PGE(2), but not MP, stimulated chondrocyte differentiation. (45)Ca accumulation in mineralizing, as compared to nonmineralizing, similarly treated control cultures was not altered by the addition of indomethacin and/or prostanoid when the phosphate source was inorganic phosphate. Because the prostanoids decrease alkaline phosphatase activity, initial beta-glycerophosphate-mediated mineralization was inhibited by each of the prostanoids.