Arachidonate activates muscle electrogenic sodium pump and brain microsome Na+,K+-ATPase under suboptimal conditions

Abstract Arachidonate 5 × 10 −5 mol·l −1 increased the rate of hyperpolarization induced in Na + -loaded mouse diaphragm fibers by 5 mmol·l −1 K + . When applied to Na + -loaded muscles without potassium, arachidonate 1 × 10 −6 and 5 × 10 −5 mol·l −1 induced a ouabain-sensitive hyperpolarization of the muscle fibers. The activity of rat brain microsomal Na + ,K + -ATPase was stimulated by 1 × 10 −7 −5 × 10 −6 mol·l −1 arachidonate in reaction media with reduced amounts of ATP or K + and after short-lasting sonication of the samples. It was concluded that, under particular conditions, arachidonate might serve as a Na + ,K + -ATPase activator or inhibitor regulating its ion transport and electrogenicity.