Regulation of Anterior Pituitary D2 Dopamine Receptors by Magnesium and Sodium Ions

Abstract
At D2 3,4‐dihydroxyphenylethylamine (dopamine) receptors in anterior pituitary tissue, magnesium ions shifted receptors to agonist high‐affinity states, but decreased the affinity of the antagonist [3H]spiperone. Conversely, sodium ions shifted the receptors to agonist low‐affinity states, but increased the affinity of [3H]spiperone. Magnesium is proposed to stabilize the hormone–receptor–guanine nucleotide regulatory protein complex, whereas sodium appears to destabilize this ternary complex. Thus, magnesium and sodium appear to mediate their regulatory effects via a common component at the D2 dopamine‐receptor ternary complex.

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