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Biomedical subjects

R Bruntink

Publications and source records attributed to R Bruntink.

5 recordsLinked to original sources
PubMed1989

Adrenal and sympathetic catecholamines in exercising rats.

The effects of adrenodemedullation and/or adrenoceptor agonists and antagonists on plasma epinephrine (E) and norepinephrine (NE) concentrations during exercise were investigated in rats. Exercise consisted of strenuous swimming against a countercurrent for 15 min in a pool with water of 33 degrees C. Before, during, and after swimming, blood samples were taken through a permanent heart catheter. E was not detectable in plasma of adrenodemedullated (Adm) rats. A marked reduction in the normal exercise-induced increase in plasma NE concentrations occurred in both Adm rats as well as in intact rats injected with the beta 2-selective adrenoceptor antagonist ICI 118551. Intravenous infusion of either E or the beta 2-selective agonist fenoterol restored the increase in plasma NE in Adm rats. Injection of the alpha 2-selective antagonist yohimbine in combination with infusion of the beta 2-selective agonist fenoterol into Adm rats caused an enormous increase in plasma NE. It is concluded that all NE in plasma as released during exercise originates from the peripheral nerve endings of the sympathetic nervous system. Adrenal E influences the release of NE via activation of presynaptic beta 2-adrenoceptors.

Adrenal Medulla↗
PubMed1989

Sympathoadrenal influence on glucose, FFA, and insulin levels in exercising rats.

The effects of sympathoadrenal manipulations on the exercise-induced alterations in blood glucose, plasma free fatty acids (FFA), and insulin were investigated in intact and adrenodemedullated rats. Exercise consisted of strenuous swimming against a countercurrent for 15 min. Before, during, and after swimming, blood samples were taken through a permanent heart catheter. Adrenodemedullation (Adm) markedly reduced the exercise-induced increase in both glucose and FFA. This effect was counteracted by intravenous infusion of epinephrine (E, 20 ng/min). Intravenous infusion of 50 ng E/min into Adm rats caused an exaggerated increase in glucose. In two additional experiments 1) specific adrenoceptor agonists and antagonists were administered to exercising intact and Adm rats, and 2) E or norepinephrine (NE; 20 ng/min) was infused into intact resting rats. The results suggest that E from the adrenal medulla directly affects glucose and insulin but not FFA concentrations in the blood. NE released from peripheral sympathetic nerve endings probably acts in two different ways: as neurotransmitter on liver and pancreas and as a hormone on adipose tissue.

Adrenal Medulla↗
PubMed1989

Experience affects exercise-induced changes in catecholamines, glucose, and FFA.

The interference of the experimental conditions on the exercise-induced alterations in plasma catecholamines, plasma free fatty acids, and glucose and insulin concentrations was investigated in rats. Exercise consisted of strenuous swimming against a countercurrent (0.22 m/s) for 15 min in a pool with water of 33 degrees C. Before, during, and after swimming, blood samples were taken through a permanent heart catheter. The blood component levels in rats that were confronted with exercise for the very first time were compared with the levels in rats that were well accustomed to the exercise conditions. The very first time rats swam caused an enhanced release of epinephrine from the adrenal medulla and a reduced output of norepinephrine from the sympathetic nerve endings. Furthermore, in the first time swim group, blood glucose levels were higher and plasma free fatty acid concentrations were lower compared with the well-accustomed animals. There were no differences in plasma insulin concentrations. It is concluded that the experimental conditions may interfere considerably with the hormonal and metabolic response to exercise. Furthermore the results reinforce the idea that the two parts of the sympathoadrenal system are functionally and metabolically dissociated.

Animals↗