The influence of body core temperature and peripheral temperatures on oxygen consumption in the pig

Abstract

SUMMARY1. The rate of oxygen consumption was measured in young pigs exposed to different ambient temperatures and the effect on metabolic rate of changing the temperature of thermodes implanted in the hypothalamus and over the spinal cord was determined. In some experiments the temperature of the skin over the trunk was changed by means of a waterperfused coat.2. Cooling the hypothalamus or the spinal cord in a warm ambient did not change the rate of oxygen consumption. At a thermoneutral ambient temperature, cooling either thermode increased oxygen consumption. In a cold environment, cooling either thermode increased the rate of oxygen consumption more than at a thermoneutral temperature. The increase in the rate of oxygen consumption was greatest during cooling of the spinal cord and it appeared that the pigs also shivered more violently. Heating either thermode tended to decrease oxygen consumption in a cold environment.3. In pigs with thermodes both in the hypothalamus and over the spinal cord, cooling both thermodes was accompanied by a greater increase in oxygen consumption than cooling either thermode alone. The increase in oxygen consumption on cooling one thermode could be reduced by heating the other.4. The skin temperature (fixed by the water perfused coat, or the ambient temperature) at which the rate of oxygen consumption increased, was lowered during heating of the thermodes, but the rate of increase in oxygen consumption appeared not to change as a function of falling skin or ambient temperature.

Changes in plasma noradrenaline and adrenaline associated with central and peripheral thermal stimuli in the pig.

“…However, a more pronounced increase in plasma noradrenaline was observed when the spinal cord was cooled. This greater response to spinal cooling is paralleled by the greater increase in metabolic rate during spinal cooling than during cooling of the hypothalamus (Carlisle & Ingram, 1973). The precise significance of these differences cannot be assessed since the exact temperature of the temperature-sensitive neurones was not known, but it seems unlikely that the neurones in the cord were cooler at a thermode temperature of 20 C than those in the hypothalamus were at a thermode temperature of 10 'C.…”

The significance of deep body temperature in regulating the concentration of thyroxine in the plasma of the pig

“…First, the magnitude of the other thermoregulatory responses observed in the pig after cooling the hypothalamus all increase steadily as the temperature of the thermode changes (Ingram & Legge, 1971Carlisle & Ingram, 1973a), while the response of the thyroid gland seems to be limited to experiments in which the thermode was cooled to 10°C. In investigations involving the rat (Reichlin, 1964) and the goat (Andersson et al 1962) the effects of different degrees of cooling were not systematically assessed, but since there was an appreciable rise in body temperature it is probable that 168 THYROID AND BODY TEMPERATURE the stimulus was a strong one.…”

The effect of developmental temperature on morphology, energy metabolism, growth hormone and thyroid stimulating hormone in Long-Evans rats

“…The maintenance of the higher metabolic rate also requires adrenal gland secretions, (13,18,45). Experiments have shown that thyroid hormone· production is counterbalanced by peripheral qegradation .of extrathyroidal hormone which increases as ambient temperature decreases and vice versa, (7,8,9,16,24,25,26,70). Thus the thyroid gland behaves·as though its secretion were essential to the internal environment through a compensatory homeostatic increase in the production of thyroid stimulating hormone when thyroid utilization increases, (16,70).…”