Trend of being deficiency in K among rural people in the northeast region of Thailand have been repeatedly demonstrated. Furthermore, its pathological roles underlying various metabolic diseases commonly seen in this region have been also proposed. In this study we measured K as well as Mg in serum, 24-hour urine and external oblique skeletal muscle of male renal stone formers (n=30) with an age ranged of 20-70 years. The results showed that 13%, 7%, 60% and 90% of the subjects had hypokalemia, hypomagnesemia, hypokaliuria and hypomagnesiuria, respectively. Using the value of mean ?0.5 SD of K content in the analyzed muscles, we divided the renal stone subjects into two groups

low muscle K content group 1 (n=15, K content ? 60.5 umol/g wet wt.) and high muscle K content group 2 (n=15, K content 68.5 umol/g wet wt.). Other renal disease subjects i.e., 3 penis tumors, 1 bladder tumor and 1 renal tumor were used as the control group 3 (n=5, K content ? 68.5 umol/g wet wt.). The means of the muscle contents among group 1, group 2 and group 3 for K were 53.49?1.67, 77.09?1.62 and 77.49?1.96 ?mol/g wet wt. and for Mg were 5.32?0.18, 7.28?0.16 and 7.15?0.22 ?mol/g wet wt., respectively. Group 1 had muscle K and Mg content lower significantly (P<0.001) than group 2 and group 3. When the values of all groups were combined, regression analysis showed that the two parameters were closely correlated (r=0.867, P<0.001) similar to other reports. Besides the analysis for K and Mg content of the muscle, Na,K-ATPase activity was also assayed by an indirect method of measuring the K dependent-3-O-MFPase activity. The results showed that group 1 had the activity ratio of K dependent-3-O- MFPase to total 3-O-MFPase lower than group 2 (P = 0.014) and group 3. The muscle contents of K and Mg among the three groups were closely correlated with Na,K-ATPase activity (r=0.530, P<0.001 for K content and r=0.464, P<0.001 for Mg content). The results suggested that both K and Mg depletions could induced downregulation of the Na,K-ATPase activity. In a preliminary study of Na,K-ATPase expression in the muscle of renal stone subjects by the dot blot and Northern blot analysis. The dot blot analysis demonstrated that the signal expression of ?2 and ?1 subunits of the enzyme was strong but of ?1 subunit was only weakly. The Northern blots analysis showed that each ?1, ?2 and ?1 hybridized to a single sizes of 2.0, 5.3, and 2.5 Kb, respectively. In addition, the human 18S ribosomal RNA (1.8 Kb) was chosen to normalize isoform-specific hybridization signals in RNA analysis. Further study should be made in order to explain the association of K and Mg depletion with the expression of the isoforms of Na,K-ATPase and to gain more understanding about the relationship between the K and Mg depletion and the pathogenesis of some metabolic diseases commonly found in this region.