UDP-SUGAR METABOLISM IN SWARM RAT CHONDROSARCOMA CHONDROCYTES

UDP-sugars and adenine nucleotides were extracted from freshly isolated chondrocytes and primary cell cultures and analysed by anion-exchange h.p.l.c. The pool sizes of UDP-N-acetylglucosamine, UDP-N-acetylgalactosamine, UDP-glucosegalactose, UDP-glucuronate and UDP-xylose were 2.9, 1.2, 2.5, 0.6 and 0.03 nmol/10(6) freshly isolated chondrocytes. When chondrocytes were maintained in Dulbecco's modified Eagle medium supplemented with 15 % foetal-bovine serum, synthesis of [S-35]proteoglycan and [H-3]protein decreased over the first 48 h in culture, as did the pools of UDP-glucuronate and ATP. In contrast, the size of the UDP-N-acetylhexosamine pools underwent little change during culture. [S-35]Proteoglycan and [H-3]protein syntheses were stimulated in cultures supplemented with serum or insulin compared with those maintained in medium alone. in agreement with previous results. However, the UDP-sugar pool sizes were the same in both supplemented and nonsupplemented cultures. In cultures maintained in the presence of [1-H-3]glucose, the UDP-sugars were labelled to a constant H-3 specific radioactivity which was very similar to that of the labelling medium. UDP-N-acetylhexosamines were labelled to constant 3H specific radioactivity with [6-H-3]glucosamine as a precursor, but only about 1 in 375 of these UDP-sugars was derived from the amino sugar in the presence of glucose. The half-life (t1/2) for UDP-hexoses, UDP-glucuronate and UDP-N-acetylhexosamines was about 12, 12 and 50 min respectively.