Tissue digoxin concentrations at digoxin intoxication in normal, acutely hypokalemic, and acutely hyperglycemic dogs.

Thirty intact dogs were studied to determine digoxin concentration in various tissues after ventricular tachycardia had been induced by digoxin infusion. A control group was infused solely with digoxin. A second group was made acutely hypokalemic by glucose-insulin infusion before the digoxin infusion. A third group was infused with glucose and digoxin to determine the effect of increased blood glucose levels and osmalarity on the induction of ventricular tachycardia. Results were: (1) The amount of digoxin infused to produce ventricular tachycardia did not differ getween the normal and hypokalemic groups. (2) The concentration of digoxin in various parts of the heart, other muscle tissue, renal cortex, and liver did not differ between the normal and acutely hypokalemic dogs although the amount excreted in bile and urine was reduced in hypokalemia. (3) Acute hypokalemia did not sensitize the myocardium to the arrhythmogenic effects of digoxin. (4) Ventricular tachcardia occurred at a similar plasma digoxin level in normal and acutely hypokalemic dogs. (5) In dogs with a lowered plasma potassium level, junctional tachycardia occurred whereas it did not occur in normal dogs or those with only a high blood glucose level. (6) Ventricular tachycardia occurred in the hyperglycemic dogs at a plasma digoxin level of 170 ng/ml, which was significantly greater than in the other experiments (7) Acute hyperglycemia reduced the mean rate of myocaridal uptake of digoxin into atria and right and left ventricular tissue; and the concentration of digoxin in atria, left ventricle, and interventricular septum was lower at the time of ventricular tachycardia than occurred in normal dogs. (8) Lowering the plasma potassium level in the presence of acute hyperglycemia, which occurred with the glucose-insulin infusion, did increase the myocardial uptake of digoxin. Similar effects of hyperglycemia were noted on mean hepatic uptake and excretion of digoxin and also the renal uptake of the glycoside.