Active Na—K transport and the rate of ouabain binding. The effect of insulin and other stimuli on skeletal muscle and adipocytes

Abstract

SUMMARY1. The effect of stimulation or inhibition of active Na-K transport on [3H]ouabain binding has been investigated in isolated soleus muscles and adipocytes.2. In rat soleus muscle, the ouabain-sensitive component of 42K influx was stimulated by insulin (100 m-u/ml.), adrenaline (6 x 106 M), and by pre-incubation with veratrine (10-5 M) or in a K-free buffer. In all of these instances, the rate of ouabain binding was increased by 41-113%. Conversely, pre-treatment with tetracaine (0.2 mM) decreased the 42K-influx and diminished the rate of [3H]ouabain binding by 36 %.3. Neither insulin, adrenaline or tetracaine produced any detectable change in the total number of ouabain-binding sites (as measured under equilibrium conditions) in rat soleus muscle.4. In mouse and guinea-pig soleus muscle and in fat cells isolated from rats, insulin also increased the rate of [3H]ouabain binding without producing any significant change in the total number of ouabain-binding sites.5. Both in soleus muscle and the epididymal fat pad of the rat, there was a linear correlation between 42K influx and the initial rate of [3H]-ouabain binding.6. It is concluded that the rate of ouabain binding is determined significantly by the rate of active Na-K transport, but within the time intervals studied (4-6 hr) stimulation or inhibition of the Na pump does not lead to any appreciable change in the total number of Na pumps. It seems unlikely that the stimulation of active Na-K transport by insulin or adrenaline is due to unmasking or de novo synthesis of Na pumps.

Thyroid hormones and the energetics of active sodium‐potassium transport in mammalian skeletal muscles.

“…In the control muscles a site number of 624 + 19 p-mole . g wet wt.-1 was found, a value slightly above that reported earlier (Clausen & Hansen, 1977). The site number was modified in muscles from hypothyroid and hyperthyroid animals in the same proportion as AJ42K.…”

Effect of Diabetes on Cytosolic Free Ca2+ and Na+-K+-ATPase in Rat Aorta

“…The fact that hypoinsulinemia causes a decrease in Na + -K + -ATPase activity was not unanticipated. From pioneering work of Clausen and Hansen (7) and Moore (8), it has been well-recognized that insulin stimulates Na + -K + -ATPase in various tissues (2,(7)(8)(9). Insulin, along with catecholamines, is considered to be the principal mediator of acute hormonal control of Na + -K + -ATPase (10).…”

Muscle cell electrical hyperpolarization and reduced exercise hyperkalemia in physically conditioned dogs.

“…Although this change is difficult to interpret, insulin appears to play an important role in sodiumpotassium transport in a number of tissues. Insulin receptor density in monocytes increases as a result of training (39); Although the specific effect of endurance training on insulin receptors has not been studied in muscle, studies on skeletal muscle of various species have shown that independently of glucose, insulin hyperpolarizes cells (40), stimulates K uptake (41), increases Na,K-ATPase activity (42), augments [3H]-ouabain binding (43), enhances affinity of pump sites on the inner membrane surface to sodium ions (44,45), and may multiply pump sites (46). Most recently, evidence has been cited that insulin facilitates Na'-proton exchange (47), allowing Na' to stimulate the pump, which generates electronegativity.…”