ISSN:
1432-2013
Schlagwort(e):
Maximal oxygen consumption
;
Cold
;
Exercise
;
Thyroidectomy
;
Plasma
;
Catecholamine
;
Glucose
;
FFA
;
Lactic acid
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Abstract Comparisons have been made in 7 dogs between maximum oxygen consumption recorded before (N dogs) and after thyroidectomy (T dogs). The comparisons were performed under two conditions 1) during severe cold stress (C $$V_{O_2 }$$ max), 2) during a short period of exhaustive work (Ex $$\dot V_{O_2 }$$ max). Heart rate, plasma catecholamine and substrate concentrations (glucose, lactic acid, FFA) were measured under each condition. 1. Thyroidectomy induced a more substantial decrease in C $$\dot V_{O_2 }$$ max than in Ex $$\dot V_{O_2 }$$ max. 2. At C $$\dot V_{O_2 }$$ max, average plasma epinephrine and norepinephrine concentrations rose to a higher level in T dogs than in N dogs. In T dogs, correlations were found between plasma epinephrine concentrations and C $$\dot V_{O_2 }$$ max values, and between plasma norepinephrine concentrations and C $$\dot V_{O_2 }$$ max values. At Ex $$V_{O_2 }$$ max, average plasma norepinephrine concentrations were similar in N dogs and in T dogs, and average plasma epinephrine concentrations were not significantly different from each other. 3. At Ex $$\dot V_{O_2 }$$ max, average plasma concentrations of the various substrates were not significantly different in N dogs and T dogs. At C $$\dot V_{O_2 }$$ max, plasma FFA levels were higher in T dogs. It may be concluded that in dogs, thyroidectomy affects mechanisms which are more specifically involved in heat production than in muscular exercise. The increased catecholamine secretion in response to cold which occured in T dogs appeared merely to limit the decrease in heat production. It seems possible that increased catecholamine secretion compensates for the decreased sensitivity of β receptors to catecholamine but it cannot fully account for the effects of thyroidectomy.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00584805
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