Hormonal and pharmacological modification of plasma potassium homeostasis

Abstract

Human skeletal muscles contain the largest single pool of K+ in the body (2600 mmol, 46 times the total K+ content of the extracellular space). Intense exercise may double arterial plasma K+ in one min. This is because of excitation‐induced release of K+ from the working muscle cells via K+ channels. This hyperkalemia is rapidly corrected by reaccumulation of K+ into the muscle cells via Na+,K+ pumps, often leading to hypokalemia. Hyperkalemia may also arise from muscle cell damage, excessive oral or intravenous administration of K+, acidosis, renal failure, depolarization of muscle cells with succinyl choline, activation of K+ channels by fluoride poisoning, hyperkalemic periodic paralysis, malignant hyperthermia, inhibition of the Na+,K+ pumps by digitalis glycosides or treatment with nonselective beta blockers. Hyperkalemia may cause arrhythmia and can be treated with beta2 agonists, insulin or hemodialysis. Hypokalemia may be induced by the stimulation of the Na+,K+ pumps in skeletal muscles seen postexercise, or by catecholamines, beta2 agonists, pheochromocytoma, theophylline, caffeine or insulin, by sepsis, myocardial infarction, trauma, burns and heart failure. Rare causes are hypokalemic periodic paralysis, inhibition of K+ channels by barium, chloroquine or barbiturates. Hypokalemia often reflects dietary K+ deficiency, alkalosis, renal or gastrointestinal loss of K+. Hypokalemia is more likely to cause arrhythmia than hyperkalemia and can be treated by oral or intravenous administration of K+ under frequent control of electrocardiogram and plasma K+. Because of their size and high contents of K+, Na+,K+ pumps and K+ channels, the skeletal muscles play a central role in the acute, from min‐to‐min ongoing regulation of plasma K+. This is decisive for the maintenance of muscle contractility and heart function.

Mechanism of Thyrotoxic Periodic Paralysis

“…6 The critical role of myocyte K + efflux in extracellular K + homeostasis is supported by the finding that patients with barium (an inhibitor of skeletal muscle K + channels) poisoning develop acute hypokalemia and muscle paralysis. 6 The important role of Na + -K + ATPase pumps in the pathogenesis of TPP is supported by the finding that their activity in the skeletal muscle is significantly increased. 7 Thyroid hormone can stimulate Na + -K + ATPase in skeletal muscle by genomic mechanism, acting on the thyroid hormone responsive elements to upregulate the transcription of the gene encoding Na + -K + ATPase, and through nongenomic mechanisms by enhancing the intrinsic activity or promoting membrane insertion of the pump.…”

“…In the skeletal muscle, Na + -K + ATPase and K + channels, including inward rectifying K + (Kir) and delayed rectifying K + channels, provide the main access for inward and outward K + movements, respectively. 6 It is estimated that active uptake of K + through Na + -K + ATPase at a rate of 125 mmol/min can decrease serum K + concentration by 3 mM within 1 minute, providing that there is no concomitant K + efflux from myocytes. 6 The critical role of myocyte K + efflux in extracellular K + homeostasis is supported by the finding that patients with barium (an inhibitor of skeletal muscle K + channels) poisoning develop acute hypokalemia and muscle paralysis.…”

“…6 It is estimated that active uptake of K + through Na + -K + ATPase at a rate of 125 mmol/min can decrease serum K + concentration by 3 mM within 1 minute, providing that there is no concomitant K + efflux from myocytes. 6 The critical role of myocyte K + efflux in extracellular K + homeostasis is supported by the finding that patients with barium (an inhibitor of skeletal muscle K + channels) poisoning develop acute hypokalemia and muscle paralysis. 6 The important role of Na + -K + ATPase pumps in the pathogenesis of TPP is supported by the finding that their activity in the skeletal muscle is significantly increased.…”

Effects of a 24-h naproxen dose on hydration and electrolyte measures during moderate-intensity cycling in the heat

“…Our participants remained within normal P[K + ] levels (<5 mmol/L) (Clausen 2010). Potassium is tightly regulated by the kidneys because elevated plasma levels may cause cardiac arrhythmias and death (Clausen 2010).…”

Nanosized rods agglomerates as a new approach for formulation of a dry powder inhaler

“…20 Theophylline is used in c onjunction with small doses of beta agonists in the treatment of asthma; 21 however, this combination may cause side effects, including hypokalemia. 15,22,23 Particular care is m andatory when introducing or withdrawing drugs that i nteract with t heophylline. A plasma theophylline concentration of 10-20 mg/L is required to achieve a t herapeutic effect.…”