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.

Potassium status of Northeast Thai constructors in three different geographic locations.

Sudden and unexpected death of young adults during sleep is a phenomenon among Southeast Asians and particularly young Northeast (NE) Thailand constructors in Singapore. Survivor of sudden unexplained death syndrome (SUDS) without structural heart disease with idopathic ventricular fibrillation (VF) has been documented. Low plasma potassium (K) and depletion of K can occur simply through a reduction of K intake and are associated with increased risk of VF. The K-status of the populations was evaluated in the NE (Group 1, n=30), Bangkok (Group 2, n=48) and Singapore (Group 3, n=46). Groups 2 and 3 were further subdivided into Group 2A (worked in Bangkok < or = 1 year, n=8), Group 2B (worked in Bangkok > 1 year, n=40), Group 3A (consumed self-prepared or ready-to-buy meals, n=25) and Group 3B (regularly consumed foods provided free-of-charge by construction companies, n=21). Thirty-four male healthy university personnels from the NE and Bangkok served as the control--Group 4. Two 24-h urine samples and a fasting blood sample were collected from each subject. Dietary-K from food was determined by duplicated meal analysis. All these samples were then analyzed for their K-content. Group 3A had the lowest K-status: their K-intake, serum-K, and urinary-K level were 29 +/- 5.8 mmol/day (% low K-intake=100), 3.43 +/- 0.34 mmol/L (% hypokalemia=48) and 19.23 +/- 8.2 mmol/day (% hypokaliuria=87.5), respectively. Among the construction workers, average K-intake, serum-K and urinary-K levels were 45.5 +/- 6.1 mmol/day (% low K-intake = 37.5), 3.93 +/- 0.2 mmol/L (% hypokalemia = 2.5) and 39.6 +/- 9.2 mmol/day (% hypokaliuria = 12.5), respectively. The values of Group 2B were similar to Group 4. In addition, when the data from all of the groups were compared, there was a positive correlation between dietary-K (intake) and urinary-K (excretion) (r=0.881, p<0.001). In conclusion, NE Thailand constructors from various locations exhibited low K status with low dietary-K, high incidence of hypokalemia, and low urinary-K. From the present study, this low K status may be an important trigger factor for VF in construction workers and associated with increase risk of SUDS.

Potassium, sodium and magnesium contents in skeletal muscle of renal stone-formers: a study in an area of low potassium intake.

Skeletal muscles surgically obtained from the stone-former group (external oblique muscle; n = 202, 82 males & 120 females), control group I (external oblique muscle; n = 5, all males), control group II (rectus abdominis muscle; n = 23, all females) and control group III (quadriceps femoris muscle; n = 11, all males) were analyzed for potassium (K), sodium (Na) and magnesium (Mg) contents. Muscle samples were digested with 65 per cent HNO3 and determined for K, Na and Mg by an atomic absorption spectrophotometer. The results of analysis showed the mean K, Na and Mg (+/- S.D.) contents in mumol per one gram of fresh tissue of the stone-former group, control groups I, II and III were 73.5 +/- 16.6, 51.3 +/- 13.4 and 6.6 +/- 1.3, 77.5 +/- 3.9, 43.9 +/- 9.9 and 7.2 +/- 0.5, 83.8 +/- 27.5, 49.4 +/- 24.1 and 6.7 +/- 1.8 and 85.0 +/- 17.1, 48.5 +/- 12.1 and 6.8 +/- 1.3. Among these variables, only the K content of control group III was higher significantly (p < 0.05) than that of the stone-former group. In the stone-former group, regression analysis showed significant correlations between K and Mg contents (r = 0.856, p < 0.001) and K and Na contents (r = -0.325, p < 0.001). Due to no available data of the external oblique, we made a comparison of our results to the soleus type of skeletal muscle of normal subjects reported by Dorup et al and found that the external oblique muscle had lower mean contents of K and Mg but a higher Na content than those of the soleus. Our results were similar to the K and Mg depleted muscles obtained from the patients receiving long-term treatment with diuretic drugs. The results suggest that most of our subjects in both the stone-former and the 3 control groups were in a state of K and Mg depletion. The causes may be multifactorial, for instance low intake, high sweat loss and the existence of environmental inhibitor (s) for K transport like vanadium.

Potassium needed for maintaining its balance in healthy male subjects residing in an area of low potassium intake and with a high environmental temperature.

Low potassium (K) intake and high prevalence of hypokalemia and hypokaliuria among rural dewellers in the northeast region of Thailand have been repeatedly reported and they were speculated to be in a state of low K status. In this communication we studied K balance of 10 rural (R) and 5 urban (U) male subjects in this region during a 10-day period of semi-free-living and eating group-selected diets. While K in intake, 24-h urine and feces were measured daily in all subjects, the direct measurement of K lost in sweat was made only in one subject coded R3. These parameters were then used to calculate the K balance. The results showed that mean K intakes were 1731 +/- 138 and 1839 +/- 145 mg/day for R and U subjects, respectively. Their mean K balances, calculated by subtracting the K excretions in 24-h urine (721 +/- 129 mg/day for R and 919 +/- 186 mg/day for U) and in feces (148 +/- 25 mg/day for R and 164 +/- 21 mg/day for U) from intakes, were +860 +/- 140 and +756 +/- 222 mg/day for R and U, respectively. In the subject R3, his mean K balances without and with subtracting the sweat K excretion (451 +/- 57 mg/day), were +847 +/- 373 and +396 +/- 344 mg/day, respectively. Regression of K balance versus intake indicated that R and U subjects needed K of 832 and 884 mg/day to stay in balance. Since the study was performed during the hot season (average temperature = 35.2 +/- 2.0 degrees C at 3 pm) and sweating was clearly observed (estimated sweat volume per day was 1927 +/- 420 ml for R and 1759 +/- 408 ml for U), therefore, K balance calculated without sweat K was overestimated. This was apparently seen in the subject R3 where he actually needed K of 1203 mg/day, instead of 814 mg/day calculated without sweat K, to stay in balance. The similarities in K balance data among the two groups suggested they both had the same food habit and K status. Our results indicate that any calculation for the levels of dietary K, or probably also for other minerals, to achieve the balance could be underestimated if loss via sweat is not taken into consideration.

Potassium contents of northeastern Thai foods.

From our previous nutritional assessment, low potassium (K) intake among northeastern Thai males has been clearly demonstrated. This prompted us to undertake a survey of the K content of local foods. Food samples comprised of 57 animal and 142 plant products which were collected from various places in the northeast of Thailand. The dry ashing method was used to prepare the samples for K analysis using an atomic absorption spectrophotometer. Foods could be divided into 7 groups according to their K levels. Foods containing K > or = 1000 mg per 100 g fresh food were categorized in group 1. These were mainly foods in the legume group, i.e., soybean, cowpea and mungbean. While rice (polished) and rice products, the main staple, were in group 7, the lowest K group of less than 100 mg per 100 g fresh food. Comparison studies of the natural foods between those collected from the northeast and from the central regions of the country, and between the cooked foods purchased from the rural villages and from the urban areas of Khon Kaen municipality, showed that, for most food items, the K content was similar wherever it came from. However, when the K content in various parts or in different stages of growth of the same kind of plants or animals was compared, a great variation was clearly seen, for example, young tamarind leaves contained K in group 6 whereas ripe tamarind fruit contained K in group 1. According to our food consumption data, the analysis of food components of 48 meals taken during the hot season by 13 rural volunteers revealed that food items eaten with the highest frequencies and in the largest amount were those in the low K food groups, i.e., glutinous rice (group 7) and green papaya (group 6). Our results suggest that the low K intake of these northeast rural Thai people is not due to a low K content of foods in this region, but rather that their food habits and low socioeconomic status restricts consumption of those food items with higher K contents.

Nutritional potassium status of healthy adult males residing in the rural northeast Thailand.

Sixteen villages from rural areas of 8 provinces in the northeastern region of Thailand were randomly selected as study sites. Data on potassium (K) contents in 24-hour urine and serum samples of 93 healthy adult volunteer males aged 20-50 years old were completely collected and covered all 3 seasons of the year. The method of direct weighing of food was used to assess K intake in 13 subjects. K loss through sweat during working (9 hours) in the field was measured in 14 subjects by soaking their worn-clothes in distilled water after which K contents were measured by the flame photometry method. The results showed that the means urinary K excretion of 93 subjects were less than that of the cut-off value for normal (> or = 30 mmol/day) in all seasons of which 76.71%, 90.71% and 81.02% of the urine were categorized as hypokaliuria in the hot, rainy and cold seasons, respectively. In the case of serum K of these subjects, though the mean values were within a normal limit (> or = 3.5 mmol/l), 36.56%, 34.41% and 29.03% of the serum were classified as hypokalemia in the hot, rainy and cold seasons, respectively. In the assessment of K intake, it was clearly demonstrated that the values in all 3 seasons were much lower than that of the estimated safe and adequate daily dietary intake (ESADI) of K for the westerners (1975-5625 mg/day), i.e., the means of intake in the hot, rainy and cold seasons were only 807 +/- 172, 877 +/- 257 and 902 +/- 227 mg/day, respectively. Furthermore, K loss through sweat in the cold and the hot seasons were as high as a third (7.4 +/- 2.4 mmol/day) and a half (11.5 +/- 1.6 mmol/day), respectively, of the urinary excretion. Though the total body K contents were not evaluated in this study, our results suggest rural people in the northeast region of Thailand may be in a state of K deficiency. The severity is probably worsened in the hot season as seen from the tendency of decrease in serum K levels among 650 renal stone formers and 260 blood donors in this season.