| Abstract: | Incorporation of 3H]glucosamine into hyaluronate synthesized by chondrocyte cultures was dependent on the concentration of foetal calf serum in the culture medium. 3H]Hyaluronate levels in cultures supplemented with 2% serum, or maintained without serum, were about 60 and 43%, respectively, of that in cultures maintained with 15% serum. Addition of insulin to cultures maintained with 15% serum had no significant effect on 3H]hyaluronate synthesis. Addition of the hormone to cultures maintained with 2% serum increased 3H]hyaluronate synthesis to levels either the same (1 ng insulin/ml), or greater than (100 ng insulin/ml) that in cultures maintained with 15% serum. The 3H]hyaluronate synthesized by the cultures was of very high molecular weight irrespective of the level of synthesis. 3H]Hyaluronate formed about 12% of the total 3H]glycosaminoglycan synthesized under all culture conditions. Synthesis of 35S, 3H-labelled proteoglycan was reduced, or increased, by the same relative amounts as 3H]hyaluronate, under the different culture conditions. Incorporation of 3H]glucosamine into hyaluronate by near confluent cultures of fibroblasts derived from the Swarm rat chondrosarcoma was reduced by 50% in cultures treated with 2% foetal calf serum compared to those maintained with 15% serum. 3H]Hyaluronate synthesis by fibroblast cultures treated with 2% serum was not stimulated by addition of insulin. |
