2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
344
ADAPTATION OF ADRENERGIC FUNCTIONS IN WINTER
SWIMMERS
Ladislav Janský 1 , Stanislav Vybíral 2 , Jan Okrouhlík 1 , Milena Trubačová 2
1 Biological Faculty, University of South Bohemia, Budweis, 2 Faculty of Science, Charles
University, Prague, Czech Rep.
Contact person: janskyl@seznam.cz
INTRODUCTION
Our previous observations revealed that adaptation of humans to cold due the repeated whole
body cold water immersions induces a downward shift of the hypothalamic threshold for
induction of cold thermogenesis (hypothermic adaptation) (Janský et al. 1996, Vybíral et al.
2000). Further it was found that in cold adapted winter swimmers the adrenergic
thermogenesis was potentiated (metabolic adaptation) and vasoconstriction became more
effective (insulative adaptation) (Lesná et al. 1999). The role of the sympathetic nervous
system and adrenergic receptors in mediating these functions has been well established (for
review see Janský and Janský 2002). The question remains, whether the role of adrenoceptors
is influenced by cold adaptation. In this study we concentrated on clarifying the role of beta1
and beta2 adrenoceptors in mediating adrenergic thermogenesis and cardiovascular functions
in cold adapted winter swimmers.
METHODS
Metabolic rate, skin temperatures, rectal temperature, heart rate and systolic blood pressure
were measured in a control group (n=6, age 21,5 years, body mass 70,0 kg, height 183 cm,
body mass index 25,7) and in winter swimmers (n=6, age 42,8 years, body mass 83,0 kg,
height 179,1 cm, body mass index 25,9) at rest and after iv infusions of increasing doses (0,5;
1,4; 2,0; 4,0; 5,0 µg. min -1 . kg -1 body mass) of the adrenergic agonist with the
predominating β1 adrenergic activity (Dobutamine, PLIVA-Lachema a.s., Brno) or of the β2
agonist (Bricanyl, AstraZeneca UK Ltd) (in concentrations 0,04; 0,08; 0,16; 0,40 µg. min -1 .
kg -1 body mass). During experiments the subjects, wearing trunks, rested in bed at
thermoneutral conditions. Increasing concentrations of the β1 agonist were administered
subsequently via the permanently cannulated antecubital vein, each concentration being
infused for 10 min. The same procedure was applied in case of the β2 agonist.
Metabolic rate was measured using a modified paramagnetic oxygen analyzer (Dvořák,
Czech Rep.). Temperature sensors (HD 590, Angloy Devices, USA) were used to measure
rectal temperature and skin temperatures on the middle finger and on the chest. A
computerized data acquisition system was used to collect and analyze the metabolic and
temperature data. Heart rate and blood pressures were monitored using a cardiomonitor Eagle
3000. Experiments on controls were performed in October and experiments on winter
swimmers were performed in February.
Data are presented as means ± SEM. Statistical significance of data, obtained on controls
and winter swimmers were compared using analysis of variance (ANOVA). The post hoc
analysis of differences between means were carried out using Student´s two tailed non-paired
test with p