The effect of catecholamines on Na—K transport and membrane potential in rat soleus muscle

Abstract

SUMMARY1. The action of catecholamines on the transport and the distribution of Na and K and the resting membrane potential (EM) has been investigated in soleus muscles isolated from fed rats.2. In a substrate-free Krebs-Ringer bicarbonate buffer adrenaline (ADR) (6 x 106 M) increased 22Na efflux by 83 %, 42K influx by 34 %, and Em by 10%. Similar effects were exerted by noradrenaline (NA), phenylephrine, salbutamol and isoprenaline. The effects of ADR on Na-K transport and EM were suppressed by ouabain (10-3 M) and propranolol (10-5 M), but not by thymoxamine (10-5 M) or tetracaine (10-4 M).3. Following 90 min of incubation in the presence of ADR (6 x 106 M), the intracellular K/Na-ratio was increased threefold. NA produced almost the same change, and both catecholamines seem to induce a new steady-state distribution of Na and K which can be maintained for several hours in vitro.4. The effect of ADR on 22Na efflux and EM could be detected at concentrations down to 6 x IO-and 6 x 10-10 M, respectively, and halfmaximum increase was obtained at around 2 x 10-8 M. NA was at least one order of magnitude less potent.5. The effect of low concentrations of ADR on 22Na efflux was potentiated by theophylline (2 mM). When added together, dibutyryl-cyclic AMP and theophylline mimicked the action of ADR on 22Na efflux, 42K influx, Na/K content and EM. Ouabain (10-3 M) also suppressed the effect of dibutyryl-cyclic AMP and theophylline on Na-K transport.6. Following the addition ofouabain (10-3M), EM rapidly dropped from a mean of -71 to -63 mV, and then showed a slow linear fall for up to 4hr. 7. The hyperpolarization induced by ADR was associated with a decrease in membrane conductance, 22Na influx and 42K efflux. The time course and the response to ouabain suggests that all of these effects are secondary to stimulation of the active coupled transport of Na and K. T. CLAUSEN AND J. A. FLATMAN 8. It is concluded that in rat soleus muscle, the active Na-K transport is electrogenic and susceptible to stimulation by catecholamines via beta-adrenoceptors. This effect is mediated by adenyl cyclase activation and may account for the increase in EM and the intracellular K/Na ratio.

Biological activity of antitumoural MGBG: the structural variable

“…5 confirm this hypothesis. As previously demonstrated (Cabella et al 2001), agmatine is transported in hepatocytes by an energydependent mechanism, as ouabain, a plasma membrane deenergising agent (Clausen and Flatman 1977) proved to be an ineffective inhibitor of this process. In addition, FCCP, which collapses the electrochemical gradient of ''in situ'' mitochondria, exhibits a partial inhibition of agmatine transport, as it only excludes the entrance of the amine in the mitochondrial matrix.…”

Caffeine improves endurance in 75-yr-old citizens: a randomized, double-blind, placebo-controlled, crossover study

“…Adenosine receptors are found in most tissues, including lipocytes and skeletal muscles (11), and activation of A 1 receptors leads to inhibition of lipolysis, activation of potassium channels, reduction in the atrioventricular node conduction, and inhibition of the basal and provoked neuronal activity (29). As caffeine acts as an adenosine-receptor antagonist, caffeine ingestion can thereby lead to elevation of free fatty acids before and during exercise (5,15), decrease the extracellular potassium concentration and by this promote action potential in muscle cells (4,26,29), and provoke release of the neurotransmitter serotonin that has a possible effect in mediating the feeling of fatigue (28,32). Caffeine is also associated with elevated plasma epinephrine, and glycogen sparing does occur in the active muscle, at least in the first few minutes (13).…”

Desensitization by Terbutaline of Β‐adrenoceptors in the Guinea‐pig Soleus Muscle: Biochemical Alterations Associated With Functional Changes

“…Detailed in vitro studies on the soleus muscle from guinea-pig and rat, respectively, show that the effects on the contractions (Waldeck, 1977;AlJeboory & Marshall, 1978) and on the active Na-Ktransport (Clausen & Flatman, 1977;1980) are both mediated by P2-adrenoceptors, presumably via stimulation of adenylate cyclase (Clausen & Flatman, 1977;Al-Jeboory & Marshall, 1978;Fellenius, Hedberg, Holmberg & Waldeck, 1980).…”

“…Another well-established effect of P-adrenoceptor agonists on skeletal muscle is the stimulation of the active Na-K-transport across the plasma membrane (Clausen & Flatman, 1977;Rogus, Cheng & Zierler, 1977). Detailed in vitro studies on the soleus muscle from guinea-pig and rat, respectively, show that the effects on the contractions (Waldeck, 1977;AlJeboory & Marshall, 1978) and on the active Na-Ktransport (Clausen & Flatman, 1977;1980) are both mediated by P2-adrenoceptors, presumably via stimulation of adenylate cyclase (Clausen & Flatman, 1977;Al-Jeboory & Marshall, 1978;Fellenius, Hedberg, Holmberg & Waldeck, 1980).…”