Production and elimination of hyaluronan in rheumatoid arthritis patients:Estimation with a loading test

Objective: To evaluate the benefit of determining the maximal elimination r ate (V-max) and the endogenous production of hyaluronan (HYA) in relation t o the basal HYA concentration (c(0)) in rheumatoid arthritis (RA) patients; and to evaluate the compatibility of a new model for HYA kinetics, taking renal elimination into separate account in the overall clearance of HYA fro m the blood. Methods: The calculations of production and elimination of HYA were based o n the HYA loading test, which was performed in 21 patients with RA and 15 h ealthy controls. A blood sample was drawn before the loading test, followed by an intravenous (IV) injection of HYA as a single bolus dose of 7.5 mg. Blood samples were taken regularly during the next 60 minutes. A theoretica l model with computational analysis of the data collected was used for calc ulating HYA production and elimination. Results: Patients with RA had significantly higher co than healthy controls , although in 10 of 21 patients c(0) was within the normal range. The RA pa tients also had higher V-max than healthy controls, but the difference was not significant, The calculated production of HYA was increased in RA patie nts (P =.001) and correlated with c(0) (P <.0001). The new model for HYA ki netics, in which the renal elimination was taken separately into account, p roved to be more compatible than the previous model. Conclusion: The HYA loading test can help determine whether the increased s erum level of HYA in RA patients is due to a high production or reduced eli mination of HYA or both. Semin Arthritis Rheum 28:268-279. Copyright (C) 19 99 by W.B. Saunders Company.