Correlation between Na, K-ATPase activity and potassium and magnesium contents in skeletal muscle of renal stone patients.

Samples of external oblique muscles were surgically removed from 45 renal stone patients and analyzed for their K, Na and Mg content. The muscle samples were also measured for membrane Na, K-ATPase activity from the assay of its K+-dependent 3-0-methyl fluorescein phosphatase (K+-dependent 3-0-MFPase) activity. The results showed that the mean muscle contents +/- SEM of K, Na and Mg were 65.2 +/- 1.7 (range, 41.1 to 86.1), 45.5 +/- 2.0 (range, 23.5 to 73.2) and 6.3 +/- 1.0 (range, 4.1 to 8.5) micromol/g wet weight, respectively. The mean activity +/- SEM of the K+-dependent 3-0-MFPase or the Na, K-ATPase was calculated by subtracting the activity of the basal-form from that of the total-3-0-MFPase, which was 113 +/- 21 (range, 11 to 177) nmol/g wet weight/minute. The activity of the Na, K-ATPase showed a significant correlation with muscle K-content (r = 0.52, p<0.001) and Mg content (r = 0.45, p<0.002). Though the external oblique muscles of renal stone patients in our study, as compared to data from other sources, had a considerably low concentration of K and Mg, they exhibited a good correlation with membrane-Na, K-ATPase activity. Our results, therefore, support previous observations made by other investigators.