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Forskolin- and dibutyryl cyclic AMP-mediated inhibition of chondrogenesis.

The regulatory role of cyclic AMP in various cellular activities is well known. It has been documented that both the notochord and extracellular matrix materials (ECM) induce somite chrondrogenesis. We believe that the ECM modulates the intracellular cAMP level during chondrogenic differentiation. The studies indicated that notochordal induction, which resulted in somite chondrogenesis (reflected by increased sulfated glycosaminoglycan synthesis) reduced the intracellular cAMP level in somites. Addition of forskolin and dibutyryl cAMP resulted in increased intracellular cAMP levels and decreased synthesis of sulfated glycosaminoglycans (decreased chondrogenesis). In the case of dibutyryl cAMP, the inhibition of sulfated glycosaminoglycan synthesis was related to the length of exposure time. Thus, the inverse relationship between cAMP content and enhanced chondrogenesis supports the theory that, in somites, a decrease in the intracellular cAMP level may be necessary to trigger chondrogenic differentiation.