Cardiac muscle function following chronic dietary potassium depletion in the rabbit.
OBJECTIVE
The aim was to investigate a possible defect in cardiac muscle contractile performance following chronic K+ depletion.


METHODS
Cardiac muscle force development, membrane potential, and action potential configuration were measured in isolated superfused right ventricular papillary muscles or trabeculae from control or K+ depleted NZW rabbits. The effects of adrenaline, strophanthidin, and changes in external [Ca2+] and [K+] were investigated.


METHODS
Experiments were performed on 50 adult NZW rabbits, average weight 2.3 kg, which were fed either a control diet (n = 25), or a K+ deficient diet (n = 25) for 25 d.


RESULTS
There was a significant reduction in contractile force in preparations from the K+ depleted group compared to those from control animals. This was associated with an increased positive inotropic response to low [K+], but an apparent reduction in response to adrenaline. There was no significant difference between groups as to the effect of strophanthidin.


CONCLUSIONS
It is suggested that the reduction in response to adrenaline reflects a down regulation in beta receptor density, due to an increased level of circulating catecholamines, and that the defect in myocardial function is a result of adaptive changes to Ca2+ handling mechanisms within the cell.
Ward
J P
JP
Department of Medicine, United Medical School, London.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002908:Chronic Disease; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D011191:Potassium Deficiency / Q000503:physiopathology*; D011817:Rabbits; D013327:Strophanthidin / Q000494:pharmacology
D013327:Strophanthidin; D002118:Calcium; D004837:Epinephrine