The prostaglandins of articular cartilage. I. Correlates of prostaglandin activity in a chondrocyte culture system.

Suspensions of aggregated chondrocytes display active prostaglandin (PG) production. Radioimmunoassay of culture media and thin layer chromatographic analysis suggests that PGE2 is the primary PG synthesized. In order of decreasing concentration, the following PG were tentatively identified; PGE greater than PGI greater than PGA + PGB greater than or equal to PGF1+2 greater than TxB. An inverse logarithmic relationship was identified between PG synthesis and cells cultured at densities of 1.5 to 7.5 x 10(6) cells/ml. Little or no change in the PG distribution profile was seen at these high cell densities. Maximum PG synthesis was attained after 36 hours of incubation with persistence of high synthetic levels up to 48 hours. PGE2 production measured at various post-isolation intervals indicated an initial high rate of synthesis during the first 4 hours which decreased with time up to 24 hours. Cartilage explant organ cultures demonstrated a similar level of PG synthesis suggesting minimal effect of matrix on cellular PG production. Indomethacin (5 microgram/ml) inhibited PG synthesis by 70% within 4 hours and 85% after 24 hours of exposure. Arachidonic acid supplementation (10 microM) stimulated PG synthesis by 300%.