Nye J S, Snowman A M, Voglmaier S, Snyder S H
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
J Neurochem. 1989 Jun;52(6):1892-7. doi: 10.1111/j.1471-4159.1989.tb07273.x.
The high-affinity cannabinoid site in rat brain is an integral component of brain membranes that recognizes cannabinoids with inhibitory constants (Ki) in the nanomolar range. To clarify its physiological role, we studied the regulation of [3H]5'-trimethylammonium delta 8-tetrahydrocannabinol ([3H]TMA) binding. The site is inhibited by heavy metal ions, such as La3+, at low micromolar concentrations; divalent cations, such as Ca2+ and Mg2+, inhibit [3H]TMA binding, though at somewhat higher concentrations. In contrast, [3H]TMA binding is stimulated by Fe2+, Cu2+, and Hg2+ ions. Ascorbic acid and its analogs are also stimulators of cannabinoid binding at low micromolar concentrations. Stimulation of [3H]TMA binding by ascorbate or ions is dependent upon molecular oxygen, but is not inhibited by metabolic poisons. Metabolically stable nucleoside triphosphate analogs enhance [3H]TMA binding by different mechanisms, with hydrolysis of a high-energy phosphate bond apparently requisite for these influences. These results suggest that the cannabinoid binding site is associated with a nucleotide-utilizing protein possessing multiple regulatory subsites.
大鼠脑中的高亲和力大麻素位点是脑膜的一个组成部分，它能识别抑制常数（Ki）在纳摩尔范围内的大麻素。为了阐明其生理作用，我们研究了[3H]5'-三甲基铵δ8-四氢大麻酚（[3H]TMA）结合的调节。该位点在低微摩尔浓度下会被重金属离子（如La3+）抑制；二价阳离子（如Ca2+和Mg2+）也会抑制[3H]TMA结合，不过所需浓度稍高。相比之下，[3H]TMA结合会受到Fe2+、Cu2+和Hg2+离子的刺激。抗坏血酸及其类似物在低微摩尔浓度下也是大麻素结合的刺激剂。抗坏血酸盐或离子对[3H]TMA结合的刺激依赖于分子氧，但不受代谢毒物的抑制。代谢稳定的核苷三磷酸类似物通过不同机制增强[3H]TMA结合，这些影响显然需要高能磷酸键的水解。这些结果表明，大麻素结合位点与一种具有多个调节亚位点的核苷酸利用蛋白相关。
