Jain R K, Junaid M A, Rao S L
Department of Biochemistry, O.U, Hyderabad, India.
Neurochem Res. 1998 Sep;23(9):1191-6. doi: 10.1023/a:1020782119057.
Direct evidence for the excitotoxicity of 3-N-oxalyl-L-alpha,beta-diaminopropionic acid (ODAP), the Lathyrus sativus neurotoxin has been studied by examining the binding of chemically synthesized [2,3 3H]ODAP ([3H]ODAP) to synaptic membranes. [3H]ODAP binding to membranes was mostly nonspecific, with only a very low specific binding (15-20% of the total binding) and was also not saturable. The low specific binding of [3H]ODAP remained unaltered under a variety of assay conditions. A low Bmax of 3.2 +/- 0.4 pmol/mg and Kd 0.2 +/- 0.08 microM could be discerned for the high affinity interactions under conditions wherein more than 80-90% of the binding was nonspecific. While ODAP could inhibit the binding of [3H]glutamate to chick synaptic membranes with a Ki of 10 +/- 0.9 microM, even L-DAP, a non neurotoxic amino acid was also equally effective in inhibiting the binding of [3H]glutamate. The very low specific binding of [3H]ODAP to synaptic membranes thus does not warrant considering its interactions at glutamate receptors as a significant event. The results thus suggest that the reported in vitro excitotoxic potential of ODAP may not reflect its true mechanism of neurotoxicity.
通过检测化学合成的[2,3 3H]3-N-草酰-L-α,β-二氨基丙酸（[3H]ODAP）与突触膜的结合，对山黧豆神经毒素3-N-草酰-L-α,β-二氨基丙酸（ODAP）的兴奋性毒性进行了直接证据研究。[3H]ODAP与膜的结合大多是非特异性的，特异性结合非常低（占总结合的15 - 20%），且不饱和。在各种检测条件下，[3H]ODAP的低特异性结合保持不变。在超过80 - 90%的结合是非特异性的条件下，可识别出高亲和力相互作用的低Bmax为3.2±0.4 pmol/mg，Kd为0.2±0.08 μM。虽然ODAP能以10±0.9 μM的Ki抑制[3H]谷氨酸与鸡突触膜的结合，但即使是非神经毒性氨基酸L-DAP在抑制[3H]谷氨酸结合方面也同样有效。因此，[3H]ODAP与突触膜的极低特异性结合并不足以将其在谷氨酸受体上的相互作用视为一个重要事件。这些结果表明，所报道的ODAP体外兴奋性毒性潜力可能无法反映其真正的神经毒性机制。
