Mukhopadhyay S, Poddar M K
Department of Biochemistry, University of Calcutta, India.
Methods Find Exp Clin Pharmacol. 1990 Oct;12(8):519-25.
Exposure of adult male Albino rats to higher environmental temperature (HET) at 35 degrees for 2-12 h or at 45 degrees for 1-2 h decreases hypothalamic synaptosomal (NA(+)-K+)ATPase activity. Synaptosomal (Na(+)-K+)-ATPase activity in (a) CX of rats exposed to 35 degrees for 12 h, (b) CX and PM of rats exposed to 45 degrees for 1-2 h and also (c) in CS of rats exposed to 45 degrees for 2 h are inhibited. (Na(+)-K+)-ATPase activity of synaptosomes prepared from normal rat brain regions incubated at 39 degrees-43 degrees for 0.5-1 h decreased significantly in H and such inhibition was also observed in other brain regions (CX, CS and PM) after incubation of the tissue slices at 41 degrees-43 degrees for 0.5-1 h. Lineweaver-Burk plots indicate that (a) in vivo and in vitro HET-induced inhibition of brain regional synaptosomal (Na(+)-K+)-ATPase is coupled with a decrease in Vmax without any change in Km, (b) very high temperature (under in vitro condition) causes a decrease in Vmax with an increase of Km irrespective of the brain regions. Arrhenius plots show that there is a decrease in transition temperature (TT) in H of rats exposed to either 35 degrees or 45 degrees, whereas such decrease in TT of PM and CX regions are only observed after exposure at 45 degrees. These results suggest that heat exposure increases the lipid fluidity of synaptosomal membrane which may cause the conformational change of the membrane protein and hence inhibit the activity of synaptosomal (Na(+)-K+)-ATPase of brain regions.
将成年雄性白化大鼠置于35摄氏度的较高环境温度（HET）下2 - 12小时或45摄氏度下1 - 2小时，会降低下丘脑突触体（Na(+)-K+）ATP酶活性。暴露于35摄氏度12小时的大鼠的（a）视交叉（CX）、暴露于45摄氏度1 - 2小时的大鼠的（b）视交叉和乳头体（PM）以及暴露于45摄氏度2小时的大鼠的（c）中央杏仁核（CS）中的突触体（Na(+)-K+）ATP酶活性均受到抑制。从正常大鼠脑区制备的突触体在39摄氏度 - 43摄氏度下孵育0.5 - 1小时后，其（Na(+)-K+）ATP酶活性在高温（H）下显著降低，并且在组织切片于41摄氏度 - 43摄氏度下孵育0.5 - 1小时后，在其他脑区（视交叉、中央杏仁核和乳头体）也观察到这种抑制作用。Lineweaver - Burk图表明：（a）体内和体外高温诱导的脑区突触体（Na(+)-K+）ATP酶抑制与Vmax降低相关，而Km无变化；（b）极高温度（在体外条件下）导致Vmax降低且Km增加，与脑区无关。Arrhenius图显示，暴露于35摄氏度或45摄氏度的大鼠高温组的转变温度（TT）降低，而仅在暴露于45摄氏度后，乳头体和视交叉区域的TT才出现这种降低。这些结果表明，热暴露增加了突触体膜的脂质流动性，这可能导致膜蛋白的构象变化，从而抑制脑区突触体（Na(+)-K+）ATP酶的活性。
