Sodium Transport in the Toad Bladder
The Functional Organization of the Granular Cell: A Review
The isolated urinary bladder of the toad transports sodium actively across its epithelial layer and responds to the hormones vasopressin and aldosterone, properties which make it a useful model for the study of certain functions of the renal tubule. Sodium transport in the granular cells of the bladder is thought to involve first an energetically passive but selective entry step at the mucosal surface, the rate of which is increased after vasopressin administration. The second step in transport is considered to be active extrusion of the ion across the serosal boundary of the cell.
Recent evidence concerning the cellular pool of sodium and the site and mode of action of vasopressin suggests that this description is at best incomplete. No equally simple alternative hypothesis for the organization of sodium transport in this system is available at present.
- © 1971 American Heart Association, Inc.