Sugden D, Klein D C
Endocrinology. 1984 Feb;114(2):435-40. doi: 10.1210/endo-114-2-435.
[125I]Iodo-2-[beta-(4-hydroxyphenyl)-ethylaminomethyl]tetralone ([125I]HEAT), a selective, high affinity, high specific activity alpha 1-adrenoceptor ligand, is used to characterize alpha-adrenoceptors in the rat pineal gland. Binding of [125I]HEAT to membranes is rapid [association rate constant (Kon) = 3.1 nM-1 min-1] and readily reversible either by 100-fold dilution or by addition of excess unlabeled HEAT [apparent dissociation rate constant (Koff) = 0.153 min-1). Saturation experiments indicate a single class of noncooperative binding sites with an equilibrium binding constant (KD) of 41 +/- 9 pM and a Bmax of 399 +/- 63 fmol/mg protein. The relative potency of a number of adrenoceptor agonists and antagonists in competing with [125I] HEAT indicates the receptor is an alpha 1-subtype. In addition, inhibition of binding is stereospecific; (-)epinephrine and norepinephrine are more than 100-fold more potent than their (+)isomers. The identification of alpha 1-adrenoceptors in the pineal gland is consistent with evidence indicating a role for these receptors in the regulation of melatonin synthesis and phosphatidylinositol turnover.
[125I]碘-2-[β-(4-羟基苯基)-乙胺甲基]四氢萘酮([125I]HEAT)是一种选择性、高亲和力、高比活性的α1-肾上腺素能受体配体，用于表征大鼠松果体中的α-肾上腺素能受体。[125I]HEAT与膜的结合迅速（缔合速率常数(Kon)=3.1nM-1min-1），通过100倍稀释或加入过量未标记的HEAT均可轻易逆转（表观解离速率常数(Koff)=0.153min-1）。饱和实验表明存在一类非协同结合位点，其平衡结合常数(KD)为41±9pM，最大结合容量(Bmax)为399±63fmol/mg蛋白质。多种肾上腺素能受体激动剂和拮抗剂与[125I]HEAT竞争的相对效力表明该受体为α1亚型。此外，结合抑制具有立体特异性；(-)肾上腺素和去甲肾上腺素的效力比其(+)异构体强100倍以上。松果体中α1-肾上腺素能受体的鉴定与表明这些受体在褪黑素合成和磷脂酰肌醇代谢调节中起作用的证据一致。
