Analysis of uric acid transport in renal tubules using benzbromarone and pyrazinamide.

Both the benzbromarone loading test alone and the pyrazinamide suppression test combined with the benzbromarone loading test were performed in four healthy male volunteers to examine the renal handling of uric acid and to demonstrate whether benzbromarone selectively blocks postsecretory reabsorption. On the basis of the four-component theory, equations of four states of fractional uric acid clearance were constructed: 1) the control state, the states of 2) benzbromarone loading, 3) pyrazinamide suppression and 4) both pyrazinamide suppression and benzbromarone loading. As a result, presecretory reabsorption, tubular secretion and postsecretory reabsorption of uric acid were calculated to be about 93-98%, 30-44% and 79-92%, respectively. In addition, it was calculated that benzbromarone inhibited postsecretory reabsorption selectively. Because of the selectivity of the action site of benzbromarone in renal tubules, this loading test is considered to reflect uric acid transport more precisely than tests using probenecid.