| Popis: |
Studies both in vivo and in vitro implicate glucocorticoids in various aspects of thermogenesis and prevention of heat loss. Many or most of these effects are probably permissive. Adrenalectomized, cold-exposed rats require glucocorticoids for catecholamine-mediated mobilization of free fatty acids, for shivering responses, and for vasoconstriction and piloerection. Glucocorticoid pretreatment of hypothermic hamsters results in a physiological state more similar bioenergetically to hibernation than to hypothermia. For example, such hamsters can arouse to normothermia from a body temperature of 8 C in a 7--8 C cold room. Lipolytic, gluconeogenic, glycogenolic, and pressor actions resulting from several hormone interactions that require glucocorticoids for optimum responses may account for the enhanced thermogenic ability shown by glucocorticoid-pretreated hamsters. Glucocorticoid treatment also results in enhanced blood and liver carbohydrate levels during hypothermia, a condition similar to that occurring in naturally hibernating animals as opposed to the depleted carbohydrate reserves generally seen in hypothermic animals. |
