Role of vanadium in endemic diseases in Northeast Thailand

为了确定泰国东北部与不明原因猝死综合征（SUDS）相关的地方性疾病（包括远端肾小管酸中毒、低钾性周期性麻痹和尿路结石）的可能原因，开展了实地调查和实验室调查1。实地工作我们走访了亚索索恩地区的村民，他们的成员都患有SUDS，并进行了采访。作为分析样本，我们采集了他们的血液、尿液、水和土壤，测定了包括钒酸盐(V)在内的各种元素。1)遗传因素由于当地对SUDS的定义与临床不同，很难确定遗传素质的可能性。尽管如此，我们还是从有限数量的suds亲属中收集了血液和尿液样本，以进一步分析DNA，寻找常见QT延长综合征的异常基因。2)获取因素我们分析了东北（NE）和曼谷（BK）收集的样本中的43种不同元素作为对照。土壤和水中的钒含量NE与BK之间没有差异，而土壤中Ca、Mg、K和Pb含量BK高于NE。只有NE的Na高于NE。东北地区村民血浆和尿液中钾含量均高于bk，提示东北地区村民在低钾条件下仍能维持较高的细胞内钾含量，这种钾保持机制的紊乱可能是导致地方病发生的原因之一。动物模型实验：低钾饮食治疗时间超过1个月的大鼠出现低钾血症，心脏和肾脏功能出现异常。由于在低钾下没有发生SUDS，因此应该研究其他因素，例如低Mg。

In order to identify possible causes of sudden unexplained death syndrome (SUDS) -related endemic diseases (including distal renal tubular acidosis, hypokalemic periodic paralysis and urinary stone) in North-East Thailand, a fieldwork and laboratory investigations were carried out.1. FieldworkWe visited villagers in Yasothorn district whose members were suffered from SUDS,and made interviews. As analytical samples, their blood, urine, water and soil were collected for the determination of various elements including Vanadate (V).1) Genetic factorsSince the local definition of SUDS is different from clinical one, it was difficult to identify a possibility of genetic diathesis. Nevertheless, blood and urine samples were collected from a limited number of SUDS-relatives for further analysis of DNA to look for abnormal genes in familiar QT elongation syndrome.2) Acquired factorsWe analyzed 43 different elements in the collected samples from North-East (NE) and Bangkok (BK) as controls. Vanadium contents in soils and water revealed no difference between NE and BK,whereas contents of Ca, Mg, K and Pb in soil were higher in BK than NE.Only Na in NE was higher than NE.V contents in plasma and urine in NE villagers were higher than BK.These results suggest that even under low plasma K in NE villagers their intracellular K could be maintained at relatively high levels, and that one of causes of the endemic diseases may be disturbance of this K-retaining mechanism.2. Animal model experimentsThe treatment of rats with low potassium diet for longer time than 1 month cased hypo-potassemia, and revealed abnormality in cardiac and renal functions. Since no SUDS occurred under the hypo K,additional factors e.g.low Mg should be investigated.