Mechanisms of L-triiodothyronine-induced inhibition of synaptosomal na(+)-k(+)-ATPase activity in young adult rat brain cerebral cortex.
J Thyroid Res 2013;
2013:457953. [PMID:
24307963 PMCID:
PMC3838833 DOI:
10.1155/2013/457953]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 09/19/2013] [Accepted: 09/24/2013] [Indexed: 01/27/2023] Open
Abstract
The role of thyroid hormones (TH) in the normal functioning of adult mammalian brain is unclear. Our studies have identified synaptosomal Na(+)-K(+)-ATPase as a TH-responsive physiological parameter in adult rat cerebral cortex. L-triiodothyronine (T3) and L-thyroxine (T4) both inhibited Na(+)-K(+)-ATPase activity (but not Mg(2+)-ATPase activity) in similar dose-dependent fashions, while other metabolites of TH were less effective. Although both T3 and the β -adrenergic agonist isoproterenol inhibited Na(+)-K(+)-ATPase activity in cerebrocortical synaptosomes in similar ways, the β -adrenergic receptor blocker propranolol did not counteract the effect of T3. Instead, propranolol further inhibited Na(+)-K(+)-ATPase activity in a dose-dependent manner, suggesting that the effect of T3 on synaptosomal Na(+)-K(+)-ATPase activity was independent of β -adrenergic receptor activation. The effect of T3 on synaptosomal Na(+)-K(+)-ATPase activity was inhibited by the α2-adrenergic agonist clonidine and by glutamate. Notably, both clonidine and glutamate activate Gi-proteins of the membrane second messenger system, suggesting a potential mechanism for the inhibition of the effects of TH. In this paper, we provide support for a nongenomic mechanism of action of TH in a neuronal membrane-related energy-linked process for signal transduction in the adult condition.
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