Adenylate cyclase of human articular chondrocytes. Responsiveness to prostaglandins and other hormones

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Abstract
Adenylate cyclase [ATP pyrophosphate lyase (cyclizing), EC 4.6.1.1] is present in cultured human articular chondrocytes. Optimal conditions of incubation time, protein and substrate concentrations, and pH were determined in whole cell lysates. Maximal activity occurred at pH 8.5 with no decrease in activity up to pH 10.0. Adenylate cyclase activity of particulate membrane preparations was enhanced by the addition of crude cytosol preparations. The prostaglandins E1, E2, F1.alpha., F2.alpha., D2, B1, B2, A1 and A2, as well as adrenaline [epinephrine] and isoprenaline, stimulated adenylate cyclase derived from either adult or fetal chondrocytes. No significant stimulation was observed in the presence of human calcitonin or glucagon. Bovine parathyroid hormone always significantly stimulated the adenylate cyclase derived from fetal chondrocytes, but not from adult chondrocytes. Preincubation of the chondrocytes in culture with indomethacin and with or without supernatant medium from cultured mononuclear cells increased the responsiveness of the adenylate cyclase to prostaglandin E1.