de Lores Arnaiz G R, de Gómez de Lima M A
Instituto de Biologia Celular, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, (1121) Buenos Aires, Argentina.
Neurochem Int. 1983;5(1):117-24. doi: 10.1016/0197-0186(83)90018-9.
The activity of Na(+)?K(+)-ATPase in the membranes of nerve endings isolated from rat cerebral cortex was inhibited by dopamine. On the contrary, when the soluble fraction from cortical homogenates was added, dopamine stimulated enzyme activity. By varying the concentration of the soluble fraction present in the incubation medium for Na(+)?K(+)-ATPase assay, it was possible to establish that this fraction modulates those effects of dopamine on Na(+)?K(+)-ATPase. The preincubation of the membranes with N-ethylmaleimide under conditions in which the Na(+)?K(+)-ATPase activity was not inhibited (5 x 10(?5) M for 10 min at 37 degrees C), prevented both the inhibitory and the stimulatory effects of dopamine observed without or with the soluble fraction from brain respectively. These results suggest that dopamine probably acts on regions of the protein containing -SH groups, different from those sites responsible for the catalytic activity of the enzyme.
多巴胺可抑制从大鼠大脑皮层分离出的神经末梢膜中Na(+)?K(+)-ATP酶的活性。相反，当添加来自皮层匀浆的可溶部分时，多巴胺会刺激该酶的活性。通过改变用于Na(+)?K(+)-ATP酶测定的孵育介质中可溶部分的浓度，可以确定该部分可调节多巴胺对Na(+)?K(+)-ATP酶的这些作用。在不抑制Na(+)?K(+)-ATP酶活性的条件下（37℃下5×10⁻⁵ M孵育10分钟），用N-乙基马来酰亚胺对膜进行预孵育，可分别防止在无或有脑可溶部分时观察到的多巴胺的抑制和刺激作用。这些结果表明，多巴胺可能作用于蛋白质中含-SH基团的区域，这些区域与负责该酶催化活性的位点不同。
