Transfer of electrolytes across the urinary bladder in the dog.

The transfer of certain electrolytes (Na22, C136, K42 and P3204) from the isolated urinary bladder to the plasma compartment was studied in the dog. The rate of transfer was shown to be a function of the PH of the bladder contents over a range of 5 through 8. It was also shown that the rate of transfer was decreased by addition of common ion. Na22 and C136 showed greater rates of transfer than did P3204 and K42. However, PH influences held true for all isotopes. No active mechanism of transfer could be demonstrated and it was concluded that ion exchange was the probable explanation for the transfer process. INCE S the middle of the 19th century numerous investigators have been interested in the possibility of the passage of solutes from the lumen of the urinary bladder into the blood stream and body fluids. These early experiments produced equivocal results probably for two reasons: a) the substances employed in many cases were toxic and nonphysiological, and b) the analytical procedures were not of sufficient accuracy to determine disappearances of small magnitude from large volumes. Thus, in reviewing this subject in 1901, Cohnheim (I) concluded that the urinary bladder was impermeable to normal urinary constituents except in cases of injury or disease. Subsequently, numerous clinical reports have indicated uptake of drugs and toxic substances especially in patients with bladder disease. After the introduction of sulfanilamide, it was found that this drug, when introduced into the bladder of dogs, appeared in significant amounts in the serum (2). However, the problem of transfer of normal urinary constituents and the possible significance of this transfer in clinical problems, such as prostatic obstruction, remained unsolved. Recently, the use of radioisotopes has allowed a more physiologic approach to the study of this problem. Johnson et al. (3) demonstrated that the bladder was permeable Received for publication April I I, 1955. to water in the forms of H& and I)&. Burgess et al. (4) reported absorption from the bladder of small amounts of the radioisotopes of phosphorus, mercury and gold. The current study (using isotopic techniques) was undertaken to evaluate the rate and mechanism of transfer of normal urinary electrolytes across the urinary bladder of the dog. Na22 and CP were selected as representative of the extracellular electrolytes and I’32 (as phosphates) and K42 as representative of the intracellular group. It was soon found that many factors affected the rate and magnitude of transfer. The present paper is limited to a study of the effect of PH changes of the bladder fluid on the rate of transfer of the above-mentioned isotopes.