EFFECT OF BROMOTETRAMISOLE ON RENAL PHOSPHATE EXCRETION

Levamisole inhibits alkaline phosphatase (ALP) activity in kidney brus h border membranes and increases phosphate excretion in vivo in dogs a nd rats. l-p-Bromotetramisole (l-BR) is a more potent analog of levami sole in regard to inhibition of ALP activity in vitro, but had no effe ct on phosphate transport by in vitro proximal tubules of the rabbit, Since its effect on phosphate excretion in vivo has not been studied, the present study tested the effects of infusion of l-BR on phosphate excretion in Sprague-Dawley rats. Fractional excretion of phosphate (F E(Pl)) was measured in thyroparathyroidectomized Sprague-Dawley rats b efore and during a systemic infusion at 0.8 ml/min of 10 mM l-p-Bromot etramisole oxalate (l-BR, n = 6), or the inactive isomer d-p-Bromotetr amisole oxalate (d-BR, n = 5), The FE(Pl) increased significantly from 4.7% +/- 0.9% to 13.4% +/- 3.1% in response to l-BR whereas there wer e no changes in FE(Pl) with inactive d-BR, In conclusion, systemic inf usion of l-p-Bromotetramisole increases FE(Pl) in Sprague-Dawley rats.