Changes in intracellular ion activities induced by adrenaline in human and rat skeletal muscle

Abstract

Abstract. To study the stimulating effect of adrenaline (ADR) on active Na+/K + transport we used double-barrelled ion-sensitive micro-electrodes to measure the activities of extracellular K + (aKe) and intracellular Na + (aNai) in isolated preparations of rat soleus muscle, normal human intercostal muscle and one case of hyperkalemic periodic paralysis (h.p.p.). In these preparations, bath-application of ADR (10 .6 M) resulted in a membrane hyperpolarization and transient decreases aKe and aNal which could be blocked by ouabain (3 x 10 .4 M). In the h.p.p, muslce a continuous rise of aNal induced by elevation of aKe to 5.2 mM could be stopped by ADR. In addition, the intracellular K § activity (aKi), the free intracellular Ca 2 + concentration (pCai) and intracellular pH (pHi) were monitored in rat soleus muscle. During ADR aKi increased, pHi remained constant and intracellular Ca z § apparently decreased. In conclusion, our data show that ADR primarily stimulates the Na+/K § pump in mammalian skeletal muscle. This stimulating action is not impaired in the h.p.p, muscle.

Enhancement of K+ conductance improves in vitro the contraction force of skeletal muscle in hypokalemic periodic paralysis

“…I 1 Specimens of fiber segments (4-6 cm long) were dissected from biceps brachii, deltoid, vastus medialis or vastus lateralis muscles under local anesthesia. Such fiber segments were obtained from (1) patients who consented that a muscle biopsy be carried out for the in vitro diagnosis of susceptibility to malignant hyperthermia; (2) patients who required a musc1e biopsy for clinical diagnosis; and (3) patients with a known neuromuscular disease who consented to have a muscle biopsy for experimental reasons only. All procedures were in accordance with the Helsinki convention and the Ethics Committee of the Technical University of Munich.…”

“…The methods for the construction and calibration of the double-barrelled ion sensitive micro-electrodes (tip size 1.0-1.5 !-Lm) are described in detail elsewhere. 1 The following combinations of ionexchanger, backfilling solution, and reference solution were used: K + -sensitive micro-electrodes (Corning 477317, 200 mmol/L KCI, 1 mol/L Mg 2 + acetate); CI--sensitive micro-electrodes (WP Instruments IE-170, 200 mmol/L KCI, 0.5 mol/L K+ sulfate). For the measurement of contraction force, a muscle fiber bundle was suspended in the perspex chamber with one end fixed and the other end fastened to astrain gauge (Hottinger Baldwin, Darmstadt, FRG).…”

Relation between extracellular [K+], membrane potential and contraction in rat soleus muscle: modulation by the Na+-K+ pump

“…Insulin or CGRP did not induce any recovery of EM which suggests that other mechanisms are involved. We cannot exclude the possibility, however, that stimulation of the Na+-K + pump in deeper fibres in whole muscles decreases the [K+]0 in the adjacent interfibre space to cause repolarization in these fibres (see [2]). This effect would not occur in surface fibres where the [K+]0, adjacent to the sarcolemma, is buffered by the bulk extracellular solution.…”

Na+-K+Pump Regulation and Skeletal Muscle Contractility

“…366). Epinephrine (10 Ϫ6 M) induces ϳ10-mV hyperpolarization and a decrease in the activity of intracellular Na ϩ both in isolated rat soleus and human intercostal muscle fibers, effects that were blocked by ouabain (16).…”