Some effects of urease administration on laboratory animals

A total of 850 mice, rats, guinea pigs, and rabbits were employed in the evaluation of the acute and subacute effects of crystalline jack bean urease following single or repeated administrations. The acute ld 50 values in units per kilogram body weight for rats and mice by route of administration were: intraperitoneal (i.p.) 50; intravenous (i.v.) 20–25; and subcutaneous 50–58. The acute i.p. and i.v. ld 50 values for rabbits were 25 and 6 units, respectively. For guinea pigs the i.p. ld 50 was about 35 units. Growth of urease-treated rats and mice was equal to control whereas guinea pigs failed to grow as rapidly as their saline-treated controls. Urease-treated mice and rats had higher titers of serum antiurease than guinea pigs. Ammonia concentrations and urease activity in the gastrointestinal tract plus contents were markedly reduced in rats, mice, and guinea pigs indicating that antiurease entered the gastrointestinal tract and inhibited bacterial urease(s). No histopathological effects were noted. The toxicity was not cumulative and all survivors showed normal behavior.