Effect of acetazolamide on the otolith growth of goldfish.

In order to clarify the involvement of a functional carbonic anhydrase (CA) system in the otolith formation of the goldfish, Carassius auratus, acetazolamide, a specific CA inhibitor, was injected intraperitoneally every 3 or 4 days, and its inhibitory effect on the otolith growth was examined by means of a tetracycline labeling technique. Calcium-45 deposition on the otolith was also examind after a single injection of the drug. Given in multiple doses of 50mg per Kg of body weight, acetazolamide did not reduce the growth rate of the otolith on either dorsal or ventral side. With multiple doses of 100mg, however, the dorsal growth was significantly depressed by 17%.The ventral growth was not affected. Simialarly, calcium-45 deposition on the otolith was effectively reduced (39%) only when a dose of 100mg was given. These results suggest that, if involved, the enzyme-catalyzed hydration or hydroxylation of CO2 is not indispensable to the carbonate formation of the otolith.