Elimination and subsequent metabolism of circulating hyaluronic acid in the fetus.
Hyaluronic acid differs from other glycosaminoglycans in its lack of covalently linked peptide, absence of sulphate groups, and the exceptional size of its single-chain polymers. These differences can be related to its distinct physical and functional properties, and may be pertinent to its greater abundance in early tissue development. In mature animals, the turnover of hyaluronic acid in tissues is reflected at least partly in the blood stream. The metabolism of circulating hyaluronic acid was therefore studied in fetal sheep after intravenous injection of [3H]acetylhyaluronic acid. Between 95% and 99% was removed within 6 min. Plasma radioactivity decayed by first-order kinetics, with a half-life between 0.8 and 1.25 min. The rate of elimination did not vary materially with hyaluronic acid fractions of widely disparate average Mr or with fetal age between 70 and 120 days. 3H2O was detected in plasma within 8-10 min. Labelled material found in urine from 10 min onward included polymers greater than or equal to 70,000 Mr, which indicates that urine may be a source of hyaluronic acid in amniotic fluid. Elimination from the plasma took place mainly in the liver, where labelled material was largely recovered in small metabolic residues as early as 28 min after injection. These were shown by high pressure liquid chromatography (h.p.l.c.) to include water, acetate, N-acetylglucosamine and a fraction tentatively identified as N-acetylglucosamine 1-phosphate. Tritium radioactivity was detected in hepatic lipids but not those of the spleen. Estimated plasma turnover was in the order of 10 micrograms/min per kg body weight. This is about 3-10 times that in adult animals and is consistent with an increased inflow of hyaluronic acid generated during the maturation of developing tissues.
Fraser
J R
JR
Department of Medicine, University of Melbourne, Australia.
Dahl
L B
LB
Kimpton
W G
WG
Cahill
R N
RN
Brown
T J
TJ
Vakakis
N
N
D000653:Amniotic Fluid / Q000378:metabolism; D000818:Animals; D001826:Body Fluids / Q000378:metabolism; D005312:Fetal Blood / Q000378:metabolism*; D006207:Half-Life; D006820:Hyaluronic Acid / Q000097:blood* / Q000652:urine; D007700:Kinetics; D008099:Liver / Q000196:embryology / Q000378:metabolism; D012756:Sheep; D014018:Tissue Distribution; D014132:Trachea / Q000196:embryology / Q000378:metabolism; D014316:Tritium
D014316:Tritium; D006820:Hyaluronic Acid