Polakof Sergio, Soengas José L
Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía, Universidade de Vigo, 36310 Vigo, Spain.
J Exp Biol. 2008 Apr;211(Pt 7):1075-86. doi: 10.1242/jeb.014050.
The aim of this study was to obtain evidence in rainbow trout for a role of lactate in glucose homeostasis as well as in the function of glucosensing tissues. In a first set of experiments, trout were injected, either (1) intraperitoneally (N=8) with 5 ml kg(-1) of Cortland saline alone (control) or saline containing l-(+)-lactate (22.5 mg kg(-1) or 45 mg kg(-1)), oxamate (22.5 mg kg(-1)) or d-glucose (500 mg kg(-1)), or (2) intracerebroventricularly (N=11) with 1 microl 100 g(-1) body mass of Cortland saline alone (control) or containing d-glucose (400 microg microl(-1)) or l-(+)-lactate (400 microg microl(-1)), with samples being obtained 6 h after treatment. In a second set of experiments, hypothalamus, hindbrain and Brockmann bodies were incubated in vitro for 1 h at 15 degrees C in modified Hanks' medium containing 2, 4 or 8 mmol l(-1) l-(+)-lactate alone (control) or with 50 mmol l(-1) oxamate, 1 mmol l(-1) DIDS, 1 mmol l(-1) dichloroacetate, 10 mmol l(-1) 2-deoxy-d-glucose, 1 mmol l(-1) alpha-cyano-4-hydroxy cinnamate or 10 mmol l(-1) d-glucose. The response of parameters assessed (metabolite levels, enzyme activities and glucokinase expression) in tissues provided evidence for (1) a role for lactate in the regulation of glucose homeostasis through changes not only in brain regions but also in liver energy metabolism, which are further reflected in changes in plasma levels of metabolites; (2) the possible presence in trout brain of an astrocyte-neuron lactate shuttle similar to that found in mammals; and (3) the lack of capacity of lactate to mimic in vitro (but not in vivo) glucose effects in fish glucosensing regions.
本研究的目的是在虹鳟鱼中获取证据，证明乳酸在葡萄糖稳态以及葡萄糖感应组织功能中的作用。在第一组实验中，将虹鳟鱼（1）腹腔注射（N = 8），分别注射5 ml kg(-1) 的单纯科特兰生理盐水（对照）或含有l-(+)-乳酸（22.5 mg kg(-1) 或45 mg kg(-1)）、草氨酸盐（22.5 mg kg(-1)）或d-葡萄糖（500 mg kg(-1)）的生理盐水，或者（2）脑室内注射（N = 11），分别注射1 μl 100 g(-1) 体重的单纯科特兰生理盐水（对照）或含有d-葡萄糖（400 μg μl(-1)）或l-(+)-乳酸（400 μg μl(-1)）的生理盐水，在处理后6小时采集样本。在第二组实验中，将下丘脑、后脑和布罗克曼体在体外于15℃下在含有2、4或8 mmol l(-1) 单纯l-(+)-乳酸（对照）或含有50 mmol l(-1) 草氨酸盐、1 mmol l(-1) 二苯胺-2,2'-二磺酸、1 mmol l(-1) 二氯乙酸、10 mmol l(-1) 2-脱氧-d-葡萄糖、1 mmol l(-1) α-氰基-4-羟基肉桂酸或10 mmol l(-1) d-葡萄糖的改良汉克斯培养基中孵育1小时。对组织中评估的参数（代谢物水平、酶活性和葡萄糖激酶表达）的反应提供了以下证据：（1）乳酸不仅通过脑区变化，还通过肝脏能量代谢变化在葡萄糖稳态调节中发挥作用，这进一步反映在血浆代谢物水平的变化中；（2）虹鳟鱼脑中可能存在类似于哺乳动物中发现的星形胶质细胞 - 神经元乳酸穿梭；（3）在鱼类葡萄糖感应区域中，乳酸在体外（但不在体内）模拟葡萄糖作用的能力不足。
