8*0 to 21*1 mg with mean values of 16-7 and 10-8 mg for the two subjects.

Transcription

1 J. Phy8iol. (1973), 235, pp Printed in Great Britain DAILY LOSS OF CALCIUM AND SODIUM FROM THE SKIN OF TWO HEALTHY MEN BY T. E. F. CARR, G. E. HARRISON AND J. NOLAN From the Medical Research Council, Radiobiology Unit, Harwell, Didcot, Berkshire (Received 25 September 1972) SUMMARY 1. The daily losses from the skin of Ca and Na have been measured for two healthy men. The losses included Ca and Na in exfoliated skin cells as well as in insensible perspiration. The daily output of Ca in urine was also measured. 2. In five measurements, the total daily skin loss of Ca ranged from 8*0 to 21*1 mg with mean values of 16-7 and 10-8 mg for the two subjects. The total daily skin loss of Na under the same conditions ranged from 45 to 146 mg with mean values of 97 and 77 mg respectively. 3. The ratio of the daily skin loss to the urinary excretion of Ca was 6 8 and 3.4%. 4. There was no correlation between the daily skin loss of Ca and atmospheric humidity. 5. In the last experiment, the fraction of the total skin loss of Ca due to fluid secretion was assessed by giving an i.v. dose of47ca to each subject. The values derived for this fraction were 0*37 and INTRODUCTION The only data available on the loss of Ca from the skin by humans are for the Ca concentration in fluid collected from the skin under conditions of profuse sweating (Mitchell, Hamilton & Haines, 1949; Johnston, McMillan & Evans, 1950; Eisenberg & Gordan, 1961; Vellar & Askevold, 1968). No direct measurements appear to have been made of the total loss of Ca from the skin which will include Ca in exfoliated cells as well as Ca in the fluids secreted from the skin generally referred to as insensible perspiration or sweat. Such information is particularly relevant to the interpretation of external metabolic balances in nutritional studies and in some clinical investigations. The present investigation was designed to measure the total daily loss of Ca from the skin of two of the present authors engaged at the time in a

2 10 T. E. F. CARR, G. E. HARRISON AND J. NOLAN fairly sedentary occupation as members of the Scientific staff of the Unit. The Na loss from the skin was also measured as well as the Ca content of the 24-hr urines. In the last experiment the skin loss of an i.v. dose of 47Ca was also determined and the ratio of the fluid loss to the total skin loss of Ca was derived. METHODS (a) General. The whole body of each subject from the neck downwards including the hands and feet was covered for 24 hr periods with nylon pyjamas, socks and gloves pre-washed several times to reduce the total Ca and Na in the final wash to less than 0.1 mg. This underwear which would absorb the fluid loss and also trap the cellular debris, was covered with a nylon track suit with nylon gloves and socks pre-washed in the same way as the underwear to protect the latter from external contamination during the normal daily activity of the individuals. Galoshes were worn during the day-time. (b) Extraction of Ca and Na from the clothing. Underwear and outerwear were washed separately in a polethylene bowl by immersion for 15 min in 2 1. of decinormal hydrochloric acid warmed to about 650 C. After rinsing in distilled water and drying, the underwear and outerwear for each subject was stored until use in sealed polyethylene bags. (c) Experimental procedure. Each subject showered using a mild detergent followed by a rinse with distilled water before drying with a towel from which the available Ca had been removed by the same washing procedure as that for the clothing. He then dressed, standing in a large polyethylene-lined tray which had been pre-washed in deci-normal acid and distilled water. At the end of the experiment 24 hr later, the outer garments were removed and the subject then stepped into the polyethylene tray to remove the underwear ready for washing. The skin was rinsed with distilled water and rubbed down with a prepared sponge. This wash which did not exceed in volume was transferred to a measuring cylinder. Concentrated hydrochloric acid and distilled water were added to give 2 1. of a deci-normal solution which was used to wash the underwear. The Ca and Na content of this solution was taken as the total lost from the skin. Urine was also collected over each 24 hr experimental period. (d) Ca and Na estimations. All measurements of Ca were made by absorption flame spectrophotometry. The reproducibility of repeated estimations on a given wash was within 2 %. The Na contents were measured by emission flame spectrephotometry and repeated determination on a given wash again agreed to within 2 %. (e) Radioactive Ca injections. An i.v. dose of 1 #tc 47Ca was given to each subject in 2 ml. sterile isotonic saline 1 hr before the beginning of the last experiment to assess the fraction of the total daily skin loss of Ca which was due to fluid secretion. Previous experiments in this laboratory have shown that extracellular Ca is uniformly labelled with a radioactive marker within a few minutes after an i.v. dose to man (Harrison, Carr & Sutton, 1967). On the other hand, cells exfoliated from the skin surface were formed several days earlier in the basal skin and will be unlabelled (Rothberg, Crounse & Lee, 1961). The fraction of the total daily skin loss due to fluid secretion was determined by comparison of the specific activity of the Ca lost from the skin with the specific activity of Ca in the corresponding 24 hr urine. (f) Ca content of dry skin. Measurements were made of the Ca content of dried human skin scraped from the sole of the foot. The skin was powdered, dried in a vacuum desiccator, thermally ashed at 6000 C and dissolved in hydrochloric acid for

3 DAILY SKIN LOSS OF Ca AND Na Ca estimations. The daily loss of Ca in cellular debris estimated in the experiment in which the radioactive marker was used could thus be converted to the weight of exfoliated skin per 24 hr. RESULTS It was important to verify, (a) that 'free' Ca could be extracted from the underwear by the washing procedure, (b) that the Ca and Na extracted from the underwear was a measure of that which came from the skin and was not due to external contamination, (c) that Ca and Na from the skin was not lost by penetration to the outerwear, (d) that the Ca in the skin debris was fully extracted by warm deci-normal acid. As a test of (a), 2 ml. of a solution of Ca as chloride containing 1 mg Ca was scattered dropwise over washed sets of underwear which were then air-dried overnight and washed in deci-normal acid next day. The Ca recovered in repeated tests was mg. To test (b) and (c) an intermediate set of washed nylon pyjamas was worn by each subject during two 24 hr periods. The Ca and Na extracted from the intermediate layer of clothing was never greater than 10 % of that removed from the inner layer. These results were accepted as evidence that the Ca and Na extracted from the underwear originated from the skin and that losses by penetration of the underwear were small. To test (d) the mean Ca content per g of dried skin determined by the thermal ashing procedure described above (0.65 mg Ca per g dried skin) was compared with the extraction of Ca by warm deci-normal acid from known weights of the dried skin powder. From this comparison it was concluded that the extraction of Ca by the warm acid was almost complete ( % recovery). The body weights of the two subjects and the atmospheric conditions during each of the five experimental periods are shown in Table 1. The Ca and Na loss from the skin for the separate 24 hr periods are shown in Table 2. Correction was made to the observed values to allow for the extra loss from the surface of the head which was not included in the measurement. This correction (4 %) was calculated from the formula given by Du Bois & Du Bois (1916). The Ca content of the respective 24 hr urines and the ratio of the skin loss to the urinary excretion of Ca is also given in the Table. The daily skin loss of Ca ranged from 11-2 to 21-1 mg for and 8-0 to 13-0 mg for with respective mean valuesof 16-7 and 10-8 mg. The ratio of the skin loss to the urinary excretion of Ca for was double that for The corresponding daily skin loss of Na ranged from 45 to 146 mg for and 42 to 154 mg for with mean values of 97 and 77 mg respectively. The variation in the daily skin loss of Na was greater than that for Ca. Table 3 gives the specific activities of Ca (c/s 47Ca per mg Ca) in the 24 hr 11

4 12 T. E. F. CARR, G. E. HARRISON AND J. NOLAN skin loss and in the 24 hr urine in experiment no. 5. It is to be expected that the radioactivity lost from the skin is all due to fluid loss in perspiration, and that the specific activity of this is equal to the specific activity of the urine. It follows, therefore, that the ratio of the Ca loss in the sweat to the total skin loss of Ca is given by the ratio of the specific activity of TABLE 1. Body weights of the two subjects and the atmospheric conditions during each of the five experiments Body wt. Subject (kg) 90 Temp. 'C Experi-, ment Max. Min *4 22* Sunshine (hr) Nil 4.2 Relative humidity Rain Mid- Mid- (mm) day night Nil Nil TABLE 2. The daily loss of Ca and Na from the skin and the urinary excretion of Ca Experiment Mean Subject Skin loss per 24] hr (mg) Ca * *2 15* * * Urine Ca -., per 24 hr Na (mg) TABLE 3. Daily loss of Ca from the skin as insensible perspiration Ratio of Ca skin loss to urine Ca (%) 7.9 4* * * Specific activity of Ratio of Total daily Daily 47Ca c/s per mg Ca fluid loss of loss of Ca loss of A- Ca to total from skin Ca in fluid Subject Skin loss Urine skin loss (mg) (mg) T1.C *37 15*5 5-7 a -.H *3 3-9

5 DAILY SKIN LOSS OF Ca AND Na 13 the total skin loss to that of the urine, shown in column 4 of the table. The values derived for the Ca content of the sweat are given in column 6. DISCUSSION No excessive expenditure of physical energy took place during the experiments and the results are taken as representative of a fairly sedentary occupation. The mean daily loss of Ca in fluid secretion (Table 3) was 5x7 mg for and 3*9 mg for If the Ca content of sweat from adult man is taken as 4 mg/100 ml. and independent of the rate of sweating (Robinson & Robinson, 1954) the daily loss of fluid was 160 ml. for and 110 ml. for, estimates which are in general agreement with that of 150 ml./day made by Foster (1961) from quite different experimental data. The mean Ca content per g of human epidermis obtained by Suntzeff & Carruthers (1945) was 015 mg, almost independent of age, sex or location of the epithelial tissue. Taking the water content of human epidermis as 73 % (Eisele & Eichelberger, 1945) the Ca content derived for the dry tissue is 0-56 mg/g in satisfactory agreement with the Ca content of dried skin from the sole of the foot obtained in the present experiments (0.65 mg/g). Table 3 shows that the 24-hr loss of Ca in exfoliated cells in Expt. 5 was 9-8 mg for and 6-4 mg for corresponding to weights of 15-1 g for and 9'9 g for of exfoliated cells per 24 hr. This is greater than estimates made by Croft (1970) from the DNA content of the exfoliated cells. The present measurements of the loss of Na from the skin under conditions of normal activity can be compared with measurements made under conditions of free sweating which range from 10 to 100 m-equiv/l. (Allan & Wilson, 1971; Robinson & Robinson, 1954). If fluid secretion accounts for the major part of the Na loss from the skin and the fluid loss is taken as 160 ml. for and 110 ml. for as calculated above, the mean concentration would be 26 m-equivfl. for and 30 m-equiv/l. for, both of which fall in the range given above. There did not appear to be any obvious correlation between the rate of Ca or Na loss from the skin and atmospheric humidity. For instance in Expt. 3 (Table 1) the average humidity was 90% and the rate of Ca loss from the skin was below average for both subjects and that for Na the lowest for either subject. On the other hand, during Expt. 1 when the relative humidity was lowest, the skin losses for both elements were greater than the mean. The excretion of an i.v. dose of 45Ca in the same subjects has recently been measured up to 400 days after the injection (Carr, Harrison & Nolan,

6 14 T. E. F. CARR, G. E. HARRISON AND J. NOLAN 1973). This excretion includes not only the urinary and faecal excretion of the marker but also that lost from the skin. To derive the latter, the mean values of the ratio of total skin loss to urinary excretion of Ca for each subject, given in Table 2, were used to calculate the skin loss of 4Ca from the measured value of the urinary excretion. The skin loss calculated in this way was, for both subjects, only about 3 % of the combined urinary and faecal excretions. Isaksson & Sjogren (1965) have attempted to estimate the dermal loss of Ca from balance studies carried out on subjects under metabolic ward conditions. Their estimates even from balances carried out over 50 days range from 19 to 300 mg Ca/day. The systematic and cumulative errors in this method of indirect measurements must lead to results of doubtful significance. Our data, given above for the i.v. marker experiment, quantify the accuracy imposed in such indirect methods of the assessment of the skin loss of Ca. Some attempt has been made to check likely sources of error in the present measurements. We assess the over-all error of the present observations to be within 15 %, certainly much less than the dayto-day variations of the skin losses of Ca and Na seen in Table 2. Thus, the reason for the association of an average skin loss of Ca for in Expt. 3 with a quite low skin loss of Na remains obscure, especially as the Na loss in this experiment was the lowest for either subject. REFERENCES ALLAN, J. R. & WILSON, C. G. (1971). Influence of acclimatization on sweat sodium concentration. J. apple. Physiol. 30, CARR, T. E. F., HARRISON, G. E. & NoLAN, J. (1973). The long-term excretion and retention of an intravenous dose of 45Ca in two healthy men. Calcif. Tissue Res. 12, CROFT, D. N. (1970). Body iron loss and cell loss. Proc. R. Soc. Med. 63, Du BoIs, D. & Du BoIs, E. F. (1916). Clinical calorimetry. A formula to estimate the approximate surface area if height and weight be known. Arch8 intern. Med. 17, EISELE, C. W. & EICHELBERGER, L. (1945). Water, electrolyte and nitrogen content of skin. Proc. Soc. exp. Biol. Med. 58, EISENBERG, E. & GORDAN, G. S. (1961). Skeletal dynamics in man measured by radioactive strontium. J. clin. Invest. 40, FOSTER, K. G. (1961). Relation between colligative properties and chemical composition of sweat. J. Physiol. 155, HARRISON, G. E.. CARR, T. E. F. & SUTTON, ALICE (1967). Distribution of radioactive calcium, strontium, barium and radium following intravenous injection into a healthy man. Int. J. Radiat. Biol. 13, ISAKSSONB. & SJOGREN, B. (1965). Errors inherent in metabolic balance studies. In Proc. 2nd International Congress of Endocrinology. London Aug. 1964, pp Amsterdam: Excerpta Medica. JOHNSTON, F. A., McMnm~, T. J. & EvANs, E. R. (1950). Perspiration as a factor influencing the requirement for calcium and iron. J. Nutr. 42,

7 DAILY SKIN LOSS OF Ca AND Na 15 MITCMELL, H. H., HAMILTON, T. S. & HAINES, W. T. (1949). The dermal excretion under controlled environmental conditions of nitrogen and minerals in human subjects with particular reference to calcium and iron. J. biol. Chem. 178, ROBINSON, S. & ROBINSON, A. H. (1954). Chemical composition of sweat. Physiol. Rev. 34, ROTMBERG, S., CROUNSE, R. E. & LEE, J. L. (1961). Glycine-C-14 incorporation into the proteins of normal stratum corneum and the abnormal stratum corneum of psoriasis. J. invest. Derm. 37, SUNTZEFF, V. & CARRUTHERS, C. (1945). The mineral composition of human epidermis. J. biol. Chem. 160, VELLAR, 0. D. & AsKEVOLD, R. (1968). Studies on sweat losses of nutrients. 3. Calcium, magnesium and chloride content of the whole body cell-free sweat in healthy unacclimatized men under controlled environmental conditions. Sand. J. clin. Lab. Invest. 22,