Chankova, P.

Solakova, S.

English

Varna Medical University Press: Journals

STUDY OF T H E CIRCADIAN RHYTHM OF POTASSIUM AND SODIUM URINE EXCRETION IN SHIFT WORKERS S. Solakova, P. Chankova Key-words: circadian rhythm — potassium and sodium urine excretion — shift work — night, day and afternoon shift succession Shift work requires biological rhythm readjustment in concordance with socially determined regimen of work and rest (1, 2, 4—6). According to certain authors the rhythm of potassium urine excretion belongs to the strictly regulated bioconstants that does not change in cases of disturbances of the natural rhythm of sleep and awakeness (3). There are only scanty data in the literature available about the circadian rhythm of potassium and sodium urine excretion in shift workers. There is, therefore, reason for investigating the diurnal dynamics of the excretion of these electrolytes in workers of successive three-shift regimen of work and rest. . Material and methods A total of 46 clinically healthy men aged between 28 and 40 years with length of service between 2 and 12 years were examined in our study. They were divided into 3 groups according to the regimen of work and rest and the intervals of exami­nation. I s t — 12 shift workers from the chemical industry on successive shifts, (8 a. m. — 4 p. m.; 4 p . m . — 12 p. т . ; 0 h — 8 a. m.). Any workers were exami­ned in 4-hours intervals (10 p. m.; — 2 a. m.; 2—6 a. m.; 6—10 a. m.; 10 a. m. — 2 p. m.; 2—6 p. m.; 6—10 p. m.) during work in day, afternoon and night shift as well as in rest days. I I n d — 12 operators in command halls of the thermo-electric power-station — Varna which shifts succeed each other every three days, and 12 operators of the thermo-electric power-station — Devnya which shifts succeed each other every four days. The examinations were performed in З-hours intervals during work in day, afternoon, and night shift. I I I r d — con­trol persons of the administration-technical personnel with natural rhythm of sleep and awakeness. The examinations were done in 4-hours intervals during two successive days. Urine samples were collected after bladder emptying. In any sample potassium and sodium concentration was determined by using flame pho­tometry. The results for the corresponding time interval were processed according to the method of variation and cosinor analysis. Results and discussion Potassium urine excretion has a characteristic diurnal dynamics when con­trol persons are concerned. The minimal levels are found out during the interval between 10 p. m. and 2 a. m. (1,19=0,17 mequiv/h). Since 6 a. m. potassium con­centration increases gradually and reaches its maximum in the interval between 10 a. m. and 2. p. m. (2,37=0,25 mequiv/h) that coincides with literature data \ Study of the circadian rhythm of . . . 135 \ T a b l e 1 Circadian rhythms of electrolyte urine excretion Indexes Mesor+mean error Amplitude Acrophase Peak level Potassium mequiv/h Sodium mequiv/h 1,702-0,000 12,119-0,004 0,501 1,381 10 h 11 h 36 min a. m. 49 min a. m. 2,203 13,504 Mecf/h • Control Ш Night shift Щ Hay shift • Rest И Afternoon shift 22-2 2-6 6-/0 /6-/4 /4- /5-22 Hour Fig . 1. Daily dynamics of potassium urine excretion in shift workers (8). Sodium urine excretion is also within minimal ranges in the night (during the interval between 10 p. m. and 2 a. m.) but within maximal ones in the day interval (between 10 a. m. and 2 p. m.) (respectively 9,93 = 1,03, and 14,75=0,97 mequiv/h). In contrast to the curve of potassium urine concentration that of so­dium demonstrates an increase already during the early morning hours. The processing of the results obtained after the method of cosinor analysis introdu­ced by F . Halberg shows an expressed circadian rhythm of potassium and sodium urine excretion (table 1). Potassium and sodium urine excretion in shift workers of the first group de­monstrates also an expressed circadian rhythm with certain partial abnormalities as compared with that of individuals with natural succession of sleep and awake-ness. There is a relatively lower potassium level in workers in day and night shift (fig. 1). Its minimal values are established during the interval between 2 and 6 a. m. but not between 10 p. m. and 2 a. m. as in the control group. Sodium uri­ne concentration of shift workers is also lower in night and day shift as compared with that of the controls (fig. 2). The retention of both sodium and potassium in the organism is probably an expression of the partial external desynchronosis caused by the incoincidence of the external geophysical synchronisators (illumi­nation, air temperature and humidity etc.) and the socially determined require­ment to work in the hours of biologically reduced work capacity. It is to be noted that these partial abnormalities of the normal rhythm of electrolyte excretion are temporary and that they restore during the afternoon shift and in rest days. When the examinations were performed during the interval between 10 a. m. and 10 p. m. / 136 S. Solakova, P. Chankova in the afternoon shift and rest days as well the almost equal levels as compared with the control ones were found out. The results of the investigation of the operators in the thermo-electric power-stations show that the term of shift succession and the order of this succession • Control ЕЭ Night shift И Bay shift _ Rest _ Afternoon shift I il Meq/h i 15 17 16 15 14 • to 12 if -W 9 6 7 6 4 I 6-10 /0-/4 llt-18 /8-22 Hour Fig . 2. Dai ly dynamics of sodium urine excretion in shift workers influences on the rhythm of sodium and potassium urine excretion. The partial abnormalities in workers on three-days schedule are less expressed than those in workers on four-days one. The latter show potassium concentration of 1,94=0,2 mequiv/h in the interval between 0,30 and 3,30 a. m. that is near to the maximal level of the control group. The maximum is reached to the interval between 11,30 a. m. and 3,30 p. m. while it is in the interval between 8 and 11 a. m. when operators on three-days schedule are concerned. Some differences are also obser­ved in the cases of the afternoon shift. Potassium urine concentration of the opera­tors on three-days schedule is near to that of the controls for the intervals studied. It is possible that these differences are determined by the regimen of work and rest. According to some authors (9) organism adaptation to shift work is going on more rapidly if night shift is followed in the schedule by an afternoon but not a day one. In this cases there is a possibility to prolong the sleep thus ensuring an adaptation behaviour in the following hours of awakeness. Based on our study the following conclusions can be drawn: 1. The principal character of the circadian rhythm of potassium and sodium urine excretion remains in shift workers in spite of partial abnormalities during work in day and night shift. 2. These abnormalities are temporary and reversible. There is a restoration of the circadian rhythms during work in an afternoon shift and rest days as well. 3. The regimen of shift succession influences upon the circadian rhythm of potassium and sodium urine excretion. There are smaller abnormalities when shifts are in three-days schedules as compared with those in four-days ones. R E F E R E N C E S 1. А л я к р и н с к и й , Б . С. Биологические ритмы и организация жизни человека в Космосе. Автореф. дисс. докт. М., 1979. — 2. Д а л е в а, М., и др. В: Тр. Междунар. с.имп. катехоламини и стрес, I I . Смоленице (ЧССР), 12—16. I X . 1979 г. — З. Л о б а н, М. Study of the circadian rhythm of. 137 Биологические часы. M. , 1964, 531—545. — 4. Ц а н е в а , Н. , Г. Г а н ч е в . Тр. НИОТЛЗ, 7, 1960, 1—9. — 5. A k е r s t е d t, Т., L . T о r s v a 1. Ergonomics, 24, 1981, No 4, 2 6 5 — 2 7 4 , - 6. A k e r s t e d t , T , et a l . Sleep, 5, 1982, S 95-S 106. — 7. H a l -b e r g , F . , et a l . I n : Cellular aspects of biorhythms. Springer, 1967, 20—48. — 8. H a l -b e r g , F . Ame\ Rev. Physiol., 31 , 1969, 675—725. — 9. К n a u t h , P . J . I l m a r i -n е n. In : Experimental studies of shift work. Westdeutscher Verlag, 1975, 66—73. ИЗУЧЕНИЕ СУТОЧНОГО РИТМА ЭКСКРЕЦИИ КАЛИЯ И НАТРИЯ С МОЧОЙ У РАБОТАЮЩИХ ПОСМЕННО С. Со лакова, П. Чанкова Р Е З Ю М Е Исследовано 46 клинически здоровых мужчин, работающих в химической и энергодо­бывающей промышленности, а также и контрольная группа административно-технического персонала, работающая активно при нормальном ритме сна и бодрствования. Устанавли­вается выраженный циркадный ритм удаления калия с мочой (акрофаза отмечается в 10 ч. 36 мин), натрия (акрофаза отмечается в И ч. 49 мин.). У работающих посменно наблюдает­ся частичные отклонения от суточного ритма экскреции калия и натрия во время дневной и ночной смен, которые восстанавливаются в дни отдыха и во время послеобеденной смены. Режим труда и отдыха влияет на ритм исследованных электролитов. 

STUDY OF THE CIRCADIAN RHYTHM OF POTASSIUM AND SODIUM URINE EXCRETION IN SHIFT WORKERS

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STUDY OF THE CIRCADIAN RHYTHM OF POTASSIUM AND SODIUM URINE EXCRETION IN SHIFT WORKERS

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