E. Schoffeniels

Bioelectric potential profiles in the bladder mucosa of the tortoise Testudo hermanni hermanni Gmelin

Abstract In the herbivorous terrestrial tortoise Testudo hermanni hermanni Gmelin, the composition of blood and vesical urine indicates that the urinary bladder plays an essential part in the reabsorption of water and sodium (1, 2). This is also the case in Amphibians (3, 4), and the urinary bladder of the toad is generally assumed to act as a reservoir in the hydromineral metabolism of this species. The urinary bladder of a freshwater turtle Pseudemys scripta as well as the bladder of a terrestrial tortoise, Testudo graeca , have been shown to transport sodium actively (5, 6). Attempts to localize the sodium active transport and to explain the electrical potential difference existing in the toad urinary bladder have been made (7) but all experiments performed in this field are carried out on a complex tissue including different epithelial cells as well as blood vessels and bundles of smooth muscle fibers (9). It is therefore difficult to interpret the results as reflecting solely the activity of the epithelial cells bordering the bladder. The bladder epithelium of Testudo hermanni hermanni Gmelin can be easily isolated from the underlying tissues (9) thus giving a suitable preparation for the study of bioelectric potentials and the localization of the sodium active transport mechanism. This paper deals essentially with the determination of the electrical profile of the epithelium lining the sphincter and the urinary bladder.