Effects of Digitoxin on Exchangeable and Tissue Potassium Contents.

Abstract

Eight rabbits were injected intravenously daily for 7 days with 0.1 mg of digitoxin/kg body weight. Serial determinations of exchangeable potassium content (Ke) were made by isotopic dilution method with K42, and serum potassium concentration was determined by flame photometry. After 7 days of digitoxin the mean Ke decreased significantly from a baseline value of 207 meq,(78.7 meq/kg) to 172 meq (63.2 meq/kg). Serum K concentration at this time was significantly lower than the baseline value, having fallen from 5.35 to 4.98 meq/l. One week after discontinuation of the drug, the Ke had risen to 233 meq. Another group of 4 rabbits was given a single intravenous injection of 0.2 mg of digitoxin per kg of body weight and K42 was given intravenously. Four animals not injected with digitoxin served as controls. The animals were killed after 24 hours and analyses for radio-potassium and for total water content were performed on 18 different tissues. All tissues studied in the rabbits given digitoxin contained less K than tissues in the uninjected control animals; statistically significant decreases were observed for the diaphragm, abdominal muscle and the subcutaneous connective tissue. No significant difference in the tissue water contents was found between the 2 groups. Similar tissue changes were previously reported to follow the administration of desoxy-corticosterone acetate or cortisone to normal animals. The decrease in K content following administration of digitoxin in the manner and dosages employed in the presence study is thought to be the result of an extracardiac effect of digitoxin.