O'Shea R D, Marley P D, Mercer L D, Beart P M
Clinical Pharmacology and Therapeutics Unit, Austin Hospital, University of Melbourne, Heidelberg, Victoria, Australia.
J Auton Nerv Syst. 1992 Aug;40(1):71-85. doi: 10.1016/0165-1838(92)90227-8.
L-Glutamate is known to function as a major excitatory neurotransmitter in the mammalian central nervous system, and recent reports suggest the existence of receptors for glutamate in several peripheral tissues. In the present study, the characteristics of the binding of [3H]L-glutamate to sections of bovine adrenal gland were studied, and the localisation of this binding was investigated in adrenal glands from cow, dog, rat and guinea pig. In addition, the effects of glutamate on catecholamine release from the perfused isolated bovine adrenal gland were investigated. Binding of [3H]L-glutamate to slide-mounted sections of bovine adrenal gland was of high affinity (Kd 0.4 microM), rapid, saturable, reversible, stereospecific and to a single population of sites. The pharmacological profile of this binding site appeared to be unique, and did not correspond to any of the central receptor subtypes for glutamate so far identified. In the adrenal gland of the cow, rat and guinea pig, the binding density of [3H]L-glutamate was higher in cortex than medulla, while this pattern was reversed in the canine adrenal gland. Glutamate had no effect on the basal secretion of noradrenaline or adrenaline from the perfused isolated bovine adrenal gland, and neither glutamate nor the glutamate receptor antagonist kynurenate altered the nicotine-stimulated release of these catecholamines. These results suggest the existence of a novel peripheral binding site for glutamate in the adrenal gland. The differential autoradiographic localisation of this binding site in the adrenal glands of the various species studied may reflect different functional properties of glutamate in these species, and suggests possible roles for glutamate in the modulation of adrenal function.
L-谷氨酸是哺乳动物中枢神经系统中主要的兴奋性神经递质，最近的报道表明几种外周组织中存在谷氨酸受体。在本研究中，研究了[3H]L-谷氨酸与牛肾上腺切片结合的特性，并在牛、狗、大鼠和豚鼠的肾上腺中研究了这种结合的定位。此外，还研究了谷氨酸对灌注分离的牛肾上腺中儿茶酚胺释放的影响。[3H]L-谷氨酸与牛肾上腺载玻片切片的结合具有高亲和力（Kd 0.4 microM）、快速、可饱和、可逆、立体特异性且针对单一的位点群体。该结合位点的药理学特征似乎是独特的，与迄今鉴定的任何谷氨酸中枢受体亚型均不对应。在牛、大鼠和豚鼠的肾上腺中，[3H]L-谷氨酸的结合密度在皮质中高于髓质，而在犬肾上腺中这种模式则相反。谷氨酸对灌注分离的牛肾上腺中去甲肾上腺素或肾上腺素的基础分泌没有影响，谷氨酸和谷氨酸受体拮抗剂犬尿氨酸均未改变尼古丁刺激的这些儿茶酚胺的释放。这些结果表明肾上腺中存在一种新的谷氨酸外周结合位点。在研究的各种物种的肾上腺中该结合位点的放射自显影定位差异可能反映了这些物种中谷氨酸的不同功能特性，并提示谷氨酸在调节肾上腺功能中的可能作用。
