This chapter discusses the interaction between catecholamines and thyroid hormones in regulation of exercise metabolism in dogs. The lipolytic effect of catecholamines in vitro is markedly increased in subcutaneous adipose tissue from thyroid hormone treated the animals and reverse has been found in hypothyroid subjects. Studies have shown that a single injection of triiodothyronine (T3) or thyroxine (T4) to normal dogs results in enhanced lipid mobilization and increased body temperature (Tre) during exercise-stress, although at rest plasma free fatty acid (PFA) concentration and (Tre) were not elevated above the control values. It was demonstrated that during physical effort, a marked rise in blood level of catecholamines occurs. The present study was undertaken to ascertain the role of catecholamines in the thyroid hormone-induced changes of metabolism and body temperature during exercise in dogs. For this purpose propranolol, which inhibits the metabolic action of catecholamines, was administered before or during physical effort performed by thyroxine treated dogs.

Physical work load activates the sympathoadrenomedullar as well as the adrenocortical system in healthy subjects. This chapter focuses on the response of the sympathicus and of the adrenal to physical work load in young patients with essential hypertension at the early stage of the illness. The influence of a single submaximal physical work load (PWL) on the blood pressure, the activity of dopamine-β-hydroxylase (DBH) in the serum, and the level of the total cortisol (F) in the plasma in patients with essential hypertension and in healthy volunteers, have been observed. Following the physical work load, in the hypertensive and normotensive subjects, it was observed that there is a rise in the systolic but a decrease in the diastolic blood pressure. The normotensive and hypertensive subjects reacted by a change in their blood pressure differently to the mental and to the physical work load. On the basis of the increase of serum DBH activity and increase of total plasma cortisol during physical work load of the young patients with essential hypertension at the initial stage of the illness, an increased readiness of the sympathetic nervous system and of the adrenal to react to a physical work load is assumed in comparison with the normotensive subjects.

The activity of some of the enzymes synthesizing the adrenal catecholamines is affected by the animal's genetic endowment. Activity of these enzymes is also affected by environmental variables. Mice that have received the combined psychosocial stimulation of maternal separation during infancy and isolation after weaning have reduced activity of adrenal tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT), while animals that are group housed after weaning have increased activity of these enzymes. In rats, infant handling modifies the response to later stressful situations. This manipulation consists of removing infant pups from the mother and placing them in individual containers and then returning them to the maternity cage. The procedure might be repeated for any length of time up to weaning. When the adrenocortical response to a novel environment is examined in later life, animals that have been handled in infancy have lower plasma levels of corticosterone and return to “resting” levels rapidly than non-handled animals.