Stimulation of specific [3H]-ouabain binding to microsomal preparations from rat heart and skeletal muscle by thyroid hormones: effects of 6-hydroxydopamine

Noradrenaline and thyroid function regulate (Na+,K+)-adenosine triphosphatase independently in vivo

We investigated interactions between noradrenaline and thyroid hormone status in the regulation of (Na+,K+)-ATPase in vivo. Treatment with the beta-adrenoceptor antagonist propranolol or with the neurotoxin 6-hydroxydopamine did not prevent the increases in heart (Na+,K+)-ATPase associated with triiodothyronine treatment. Administration of methimazole did not prevent the increase in (Na+,K+)-ATPase indices in cerebral cortex and heart associated with subacute noradrenergic stimulation by yohimbine. There was no evidence for synergistic effects between thyroid hormone administration and noradrenergic stimulation by yohimbine. Thyroid hormone, unlike noradrenaline, mainly increased (Na+,K+)-ATPase activity with low affinity for ouabain. These results show that noradrenaline and thyroid hormone regulate (Na+,K+)-ATPase by largely independent mechanisms, and may regulate different populations of enzyme molecules.

Sympathetic nerve terminal destruction has no effect on specific [3H]ouabain binding to intact mouse and rat skeletal muscle

Following pretreatment with 6-OH-dopamine, the sympathetic nerve endings of the iris and skeletal muscle of mice and rats were not longer detectable by cytochemistry for noradrenaline. In the same animals, the specific binding of [3H] ouabain to intact soleus muscles was not significantly different from that measured in controls, Neither ouabain-suppressible 42K uptake nor Na-K contents were affected by chemical sympathectomy.