THE INFLUENCE OF SLEEP DEPRIVATION ON LEVELS OF SERUM HORMONES IN HEALTHY

Dos t Ii 1 M., Bohumira B ilk 0 v Ii, J. Vas k u, V. P a vii C e k, P. G u b a, 0 1 gaS 0 t 0 1 0 v Ii: The Influence of Sleep Deprivation on Levels of Serum Hormones in Healthv Calves (Technical CoDmunication). Acta vet. Bmo. 57.1988:183-190. The influence of 24 h of sleep deprivation on the blood serum concentration of aldosterone, thyrotropine, triiodthyronine, and thyroxine was studied in healthy calves. In the experiment, 14 calves (Bohemian Pied x Holstein) aged 3 months with mean body mass of 85 kg were used. Blood samples were collected from the v. jugularis externa. The concentration of hormones was measured using RIA. A sleep deprivation of 24 h led to a statistically significant (P(O. 05) increase of aldosterone and thyrotropine levels and to a significant (P(0.05) decreae of triiodthyronine. The level of thyroxine and the triiodthyronine/thyroxine ratio were not changed significantly. Calf, stress, aldosterone, TSH, T3 and T4 • The loss of afferent nervous stimulation from mechanorecep.tors of the heart ventricles as a consequence of the implantation of a total artificial heart leads to changes of both neural as well as humoral feedback control (I mac h i et a1. 1983; Vas k u et a1. 1987). Changes have been described in the levels of thyroid hormones, aldosterone, renin, catecholamines, and vasopressin (B ij c her 1 et a1. 1979; I mac h i et a1. 1983; Stanley eta1.1976; Vasku eta1.1987; Webs t e r et a1. 1978). Both the specific effects of the total artificial heart as well as non-specific stress reaction play a role in th~ changes of some hormone levels (S tan 1 e y et a1. 1976; Vas k u 1965; Web s t e r et al. 1976). To determine the influence of the latter factor this preliminary study undertook an investigation of the influence of a 24-h sleep deprivation on the serum level of selected hormones. Another aim of this study was to determine physiological values of thyroid gland hormones in calves used in total artificial heart experiments.

The loss of afferent nervous stimulation from mechanorecep.tors of the heart ventricles as a consequence of the implantation of a total artificial heart leads to changes of both neural as well as humoral feedback control (I mac h i et a1. 1983;Vas k u et a1. 1987 1978). Both the specific effects of the total artificial heart as well as non-specific stress reaction play a role in th~ changes of some hormone levels (S tan 1 e y et a1. 1976; Vas k u 1965; Web s t e r et al. 1976). To determine the influence of the latter factor this preliminary study undertook an investigation of the influence of a 24-h sleep deprivation on the serum level of selected hormones. Another aim of this study was to determine physiological values of thyroid gland hormones in calves used in total artificial heart experiments.

Materials and Methods
'lhe blood for MaSurement of aldosterone, thyrotropine -TSH, triiodothyronine -T3 and thyroxine -T4 concentration was taken from 14 clinically healthy calves (6 females. 8 males). 111e animals (Bohemian Pied x Holstein) had a mean body mass of 85 kg; their age was 3 months. 'lhe calves were restrained individually in stalls of a cOlllDOn calf-shed. 'lhe temperature in the barn at the time of sampling was 25 ·C; blood samples were collected between 10-11 a.m. daily, i.e. 2-3 h after feeding. 'lhe first sampling was the control, the second collected 24 h after sleep deprivation, was the experimental.
Sleep deprivation was induced by causing the calves to get up each hodr.
Blood was drawn by aspiration from a direct venipuncture of the v. j~ laris externa. usin~ a needle and a plastic syringe. 'lhe blood was transferred into glass test tubes and centrifuged at 2,500 r.p.m. for 20 minutes. 'lhe serum samples were placed into glass test tubes and stored at -18 ·C pending analysis (within 6 weeks).
Aldosterone concentration was measured using methods described in our previous study (D 0 s t Ii 1 et ale 1985). lbyroxine (I 4 ), triiodthyronine (I 3 ) and thyrotJ;'opine (ISH) were measured using classical RIA methods modified for laboratory requirements of the Department of Nuclear Medicine. the District Institute of National Health at Znojmo. 111e TSH concentration was determined using a specific antibody C8lbioehem -Boehringer Lot No. 142107; the hormone was labelled by ehloramin iodation using NaJ 125 made by Amersham (England) lbe separation of a binding fraction was carried out using another antibody -Riagar. 111e sensitivity of the method for TSH measurement was 1.25 mU .1-1. variation coefficient 13.5 'o.
111e T3 determination was carried out using a specific antibody from the Research Institute of Endocrinology at wbochiia. radioligand from URVJI Koiice. Another antibody -Riagar from Bioveta IvanoVice na Han8was used for separation of the binding fraction. The sensitivity of the method was 0.2 nmol.1-1 , variation coefficient 9.2 'o.
Io measure the I4 concentration. a specific antibody was employed as provided by the Institute of Experimental Endocrinology, Slovak Academy of Science in Bratislava. commercial radio ligand from tiRVJI Koiice: the separation of a binding fraction was carried out with polyethylenglycol Mr 6,000. 111e sensitivity of the method was 3.4 nmol.1-1 , variation coefficient 6.8 t.
'lhe T~/I4 ratio was calculated as the 5rtio of I3 and T4 levels in the plasma 1n nmol.l-1 and multiplied by 10 as reported by S c h e id egg e r et al. (1984). 111e means and standard deviations of the values were calculated for each experimental animal. Student' s t-test for analysis of means was used for comparison of pairs. lbe P values of less than 0.05 were considered si~i ficant (R e i sen a u e r 1970).

Results
The mean values. standard deviations J and standard errors of the means for the hormones studied, before and after 24 h of sleep deprivation are presented in Table 1 decreased by 16 %, that of T 4 by 5 % and their ratio (T 3 'T 4 ) was decreased by 11 %. The increase of aldosterone and THS levels and the decrease of T 3 were significant (P(O. 05) with regard to controls (Fig. 1).

Discussion
The results obtained from control and experimental samples are within the physiological values of these hormones which have been reported for man: aldosterone up to 400 pmol. C 1 in a resting position after a few hours rest), TSH up to The values are presented as means ± S.E.M.;* = P < 0.05 ratio of T 3' T 4 is reported to be within a range of 12-32 in adult healthy persons (both men and women) (E rfur t hand H e d n e r 1986) .
The levels of aldosterone were significantly decreased in the present group of calves when compared with our previous observations. In calves of the same age, body mass, confinement and feeding procedures, employed in a previous study. mean values of aldosterone of 85.6 -26.9 pmo1.C 1 (D 0 s t Ii I et al. 1985). However, that experiment was conducted in a different season (January 1984), whereas the present study was carried out in August 1986. These differences show the importance to consider the influence of season on plasma hormone concentrations.
Increased levels of aldosterone after 24-hours sleep deprivation can be explained by a neurosecretory response of the hypothalamus. After the release of corticotropin-releasing hormone ( corticoliberin) an increase of adrenocorticotropic hormone (ACTH) occurs which stimulates directly the cells of the zona glomerulosa of the adrenal gland, resulting in an increase in the plasma level of aldosterone (B u r c h fie I d 1985; Vas k U 1965 ).
The data of the TSH levels as a sequel to stress are in conflict. Reports of its increased secretion are few; most describe it as being inhibited (S c h rei b e r 1985) . The differing data may reflect differences in the experimental design, especially the intensity of stress, stimulus and the reaction of the individual or the species.
Even the data of the response of the thyroid hormones (T 3' T 4) on acute stress are also differing. Permanent physical stress connected with insufficient dietary energy intake leads to the drop of both T 3 and T 4 with simultaneous shift to the deiodination of thyroxine in tissues (S c h rei b e r 1985) .
Sleep deprivation of our experimental animals was also connected with greater physical activity (longer periods of standing, moving). while the amount of food offered was not changed.
The slight increase of TSH and decrease of T 3' and rr:4 foum'l in the present study is in agreement with data published of these levels in human patients suffering burn InJury. The leve1 of T 3 was decreased substantially more than that of T 4' Our study recorded a non-significant decrease was caused by the decrease of T 3 and T 4 or it is a response to stimulating influence of thyroid releasing hormone (TRH), released from the hypothalamus in response to stress reaction (B u r c h fie I d 1985; S c h r e ib e r 1985).
Regarding hormones of the thyroid gland and TSH, no data for calves of identical age and body mass category have been found in the available literature. Therefore, present data may serve as reference values for further research of hormones of animals with total artificial heart implanted and surviving for a long time. Further experimentation is needed of the link between stress and thyroid gland function.