Identification of glutamine as a hepatic factor which influence the synthesis of collagen by freshly isolated fibroblasts.

Earlier we have found that 35,000 g supernatants of liver homogenates from both normal and hypercholesterolaemic rats stimulate the synthesis of collagen by freshly isolated fibroblasts. Supernatants from the fatty livers of hypercholesterolaemic rats showed greater stimulation. In the present study we fractionated the 35,000 g supernatants using gel filtration, ion-exchange chromatography, paper electrophoresis and paper chromatography. One of the stimulating factors turned out to be glutamine. However, the concentration of glutamine was the same in normal and fatty livers suggesting that glutamine is not responsible for the greater stimulating activity found in the 35,000 g supernatants from fatty livers. Authentic glutamine increased the synthesis of collagen by 40% at a concentration of 40 mumol/l but inhibited it 80% at 4 mmol/l, which is widely used in cell culture media. There, the concentration of glutamine should be controlled carefully in tests for collagen synthesis in vitro.