Effects of prostanoid precursors and indomethacin on chick embryonic cartilage growth in organ culture.

Using the Fell technique of organ culture of 8-day chick embryo femoral and tibial rudiments, the effects of indomethacin, dihomo-gamma-linolenic acid and arachidonic acid on limb rudiment linear growth and differentiation were investigated. Indomethacin (50 and 100 mumol/l) elicited a statistically significant decrease in rudiment linear growth without affecting differentiation or cell structure. Dihomo-gamma-linolenic acid and arachidonic acid, both at 100 mumol/l, exerted no effect on limb rudiment linear growth or differentiation. From previous work, it has been shown that PGA1 and PGB1 caused a marked inhibition of linear growth, PGA1 being cytotoxic. The failure of the prostaglandin (PG) precursors to reproduce these effects suggests that PGA or PGB biosynthesis in embryonic chondrocytes plays no significant role in cartilage growth regulatory mechanisms. Moreover, the growth inhibitory effect of the PG cyclooxygenase inhibitor, indomethacin, suggests that a product of arachidonic acid metabolism via the cyclooxygenase pathway may promote cartilage growth.