Synthesis and Properties of Two New Membrane-Impermeant High-Molecular-Weight Carbonic Anhydrase Inhibitors

The synthesis and inhibitory properties and stability of two nontoxic high-molecular-weight carbonic anhydrase inhibitors (F 3500 and POBUMS) are reported. F 3500 was prepared by the covalent linkage of aminobenzolamide, a potent carbonic anhydrase (CA) inhibitor, to polyoxyethylene bisacetic acid (MW 3350). Linkage of the same inhibitor to polybutadiene maleic acid copolymer (MW 20,000) gave POBUMS. They contained on a mole percentage basis 0.11–0.28% unreacted aminobenzolamide as contaminant. F 3500 and POBUMS were approximately equipotent as carbonic anhydrase inhibitors on a weight basis withKiat 37°C for CA II and CA IV of approximately 0.5 and 10 μg/ml, respectively. They showed a maximum release of 28% aminobenzolamide when heated at 70°C for 3 days at pH 10.5 and were completely stable toward enzymatic hydrolysis (protease and peptidase at 25°C). They were not membrane permeable as judged by their inability to bind to intracellular CA II in intact red cells, nor were they actively uptaken in rat kidney slices. Rats injected with F 3500 (200 mg/kg) showed no toxicity and excreted 93% of the polymer unchanged in the urine in 3 h. The two polymers should prove useful forin vivoandin vitrostudies of selective CA IV inhibition in membranes.