EFFECTS OF SODIUM-DEFICIENT MEDIUM AND OUABAIN ON POTASSIUM EXCHANGE IN TAENIA COLT

¹ Department of Pharmacology and Toxicology, University of Mississippi School of Medicine, Jackson, Mississippi

The effect of ouabain on the movements of potassium (K) in the presence and absence of external sodium (Na) was studied in the taenia coli of guinea pig. Ouabain (2.5 x 10^-6 M) produced a loss of 21 and 64 mmol of K per kg wet weight over a 30-and 60-minute period, respectively; whereas tissues in Na-deficient medium (12 mM) lost an insignificant amount after 30 minutes and only 42.8 mmol of K per kg wet weight by 60 minutes. K⁴² uptake revealed a significant decrease in uptake with a net loss of K, whereas Na-deficient medium blocked this action of ouabain. K⁴² efflux was enhanced by ouabain under normal conditions and was unaffected by ouabain in Na-deficient media. These effects of Na on ouabain's action could be related to its binding to (Na⁺ + K⁺)- adenosine triphosphatase (ATPase), which has been reported to be stimulated by Na.