KINETICS OF CIRCULATING HYALURONAN IN HUMANS

The elimination of intravenously injected hyaluronan (HA) from the blood was investigated in 12 healthy volunteers. Three consecutive 30 min infusions of HA were given, separated by 90 min washout periods. Blood samples were taken before, during and after each infusion and the plasma HA concentration was determined. The deposition of HA was modelled according to a Michaelis-Menten kinetic model which included natural synthesis of HA. K-m and V-max was estimated to 0.34 +/- 0.13 mu g ml(-1) and 3.48 +/- 0.97 mu g min(-1) kg(-1) b.w., respectively. The endogenous input was calculated to be 24 +/- 11 mu g min(-1) and was found to correlate to the age of the subjects (P < 0.05). As the baseline HA concentration was 0.031 +/- 0.21 mu g ml(-1), the rate of elimination was linear in the normal concentration range. The calculated V-d was about 75% higher than a weight-estimated plasma volume. The total amount of HA excreted by the kidneys during the study period was 394 +/- 77 mu g, which corresponded to approximately 1.7% of the total input of HA into the circulation during the experiment.