The influence of chronic hypokalemia on myocardial adrenergic receptor densities: enhanced sensitivity to epinephrine-induced arrhythmias.
We studied the effects of a 30-day potassium (K+)-deficient diet on blood [K+] myocardial adrenergic receptor densities, serum catecholamines, and epinephrine arrhythmogenicity in adult laboratory rats (250 +/- 25 g). Within 3 days of beginning the K+-deficient diet, blood [K+] decreased by 50%. After 5 days, the myocardial alpha-1 density increased (62 +/- 2 vs 148 +/- 16 fmols/mg protein), and the total beta receptor increased (95 +/- 5 vs 273 +/- 49) without significant change in receptor affinity. However, 18-21 days of this diet was necessary to produce an increase in the duration of epinephrine arrhythmias (from 56 +/- 8 to 224 +/- 21 s). While prazosin block of the alpha-1 receptor in hypokalemic rats caused a significant, 42% reduction in arrhythmic duration and propranolol block caused a 62% reduction, both prazosin and propranolol were necessary to return arrhythmia times to normal (44 +/- 0.3 mmols/dL). Total serum catecholamines were reduced after 3 days of the diet (from 482 +/- 37 to 299 +/- 31 pg/ml) and remained depressed throughout the 30 days of the K+ diet. The results of this study indicate that prolonged restriction causes a reduction in serum catecholamines, an increase in myocardial alpha-1 and beta receptors densities, and an increase in epinephrine arrhythmogenicity. All of these changes were reversed within 5 days of initiating a normal dietary K+ intake.
Miletich
D J
DJ
Department of Anesthesiology, University of Illinois at Chicago College of Medicine, 60612-7239, USA.
Minshall
R D
RD
Albrecht
R F
RF
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced*; D002395:Catecholamines / Q000097:blood; D002908:Chronic Disease; D004837:Epinephrine / Q000494:pharmacology*; D007008:Hypokalemia / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000737:chemistry*; D051381:Rats; D011941:Receptors, Adrenergic / Q000032:analysis*; D015854:Up-Regulation
D002395:Catecholamines; D011941:Receptors, Adrenergic; D004837:Epinephrine