Effects of serum and insulin on hyaluronate synthesis by cultures of chondrocytes from the Swarm rat chondrosarcoma.

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.