Excretion of HCO3- by the urinary bladder of Bufo marinus in metabolic alkalosis.

We studied the role of the urinary bladder of Bufo marinus in the excretion of bicarbonate into the urine. The toads were in metabolic alkalosis, produced by administering 120 mM NaHCO3 by stomach tube or by soaking the toads in 120 mM NaHCO3 solution for 48 to 72 hr. In vitro 10 cannulated whole bladders from toads in alkalosis transported bicarbonate from the serosal to mucosal medium. The average gradient created by this transport was 5.7 meq/1. In 15 whole bladders from toads in metabolic acidosis studied under identical conditions, there was no transport of bicarbonate into mucosal medium.