Diminished epinephrine response to hypoglycemia despite enlarged adrenal medulla in trained rats

Stallknecht, Bente; Kjær, Michael; Mikines, K. J.; Maroun, Lisa Leth; Ploug, Thorkil; Ohkuwa, Tetsuo; Vinten, J.; Galbo, H.

doi:10.1152/ajpregu.1990.259.5.r998

Cited by 30 publications

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“…In contrast to our observations, other researchers observed substantially enlarged adrenal medullas in animals and man after exercise training [41,42,43]. However, in those cases subjects were subjected to either high-intensity exhaustive exercise (cf.…”

Section: Discussioncontrasting

confidence: 99%

“…However, in those cases subjects were subjected to either high-intensity exhaustive exercise (cf. man [41]) or forced to run in a treadmill usually on a cumulative performance schedule [42,43,44]. These observations further underscore that the voluntary exercise paradigm is not comparable with those models and that exhaustive exercise induces changes which go beyond the ones seen in either mice [17, 18] or rats [present study] after voluntary exercise.…”

Section: Discussionmentioning

confidence: 82%

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Voluntary Exercise Impacts on the Rat Hypothalamic-Pituitary-Adrenocortical Axis Mainly at the Adrenal Level

Droste

Chandramohan²,

Hill³

et al. 2007

Neuroendocrinology

131

143

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Introduction: Evidence is accumulating that the regular performance of exercise is beneficial for stress coping. However, the hypothalamic-pituitary-adrenocortical (HPA) axis of voluntarily exercising rats has never been comprehensively investigated. Methods: Therefore, male Sprague-Dawley rats were given access to a running wheel in their home cage for 4 weeks in which they ran 4–7 km per night. Results: After 4 weeks, the exercising animals showed significantly less body weight gain, less abdominal fat tissue, decreased thymus weight, and increased adrenal weight (relative to body weight). Furthermore, tyrosine hydroxylase (TH) mRNA levels were selectively increased in the right adrenal me- dulla indicating an increase in sympathoadrenomedullary capacity in exercising rats. No changes were observed in paraventricular corticotropin-releasing hormone (CRH), arginine-vasopressin (AVP) and oxytocin mRNA levels. Mineralocorticoid receptor (MR) mRNA levels in hippocampus and glucocorticoid receptor (GR) mRNA levels in frontal cortex, parvocellular paraventricular nucleus and anterior pituitary were unchanged, whereas GR mRNA levels were increased in distinct hippocampal cell layers. Early morning baseline levels of plasma ACTH and corticosterone were similar in both groups. Interestingly, the response to different stressful stimuli (e.g. forced swimming, novelty) revealed that the exercising rats showed stressor-specific changes in HPA hormone responses. Forced swimming evoked a markedly enhanced response in corticosterone levels in the exercising rats. In contrast, if rats were exposed to a novel environment, exercising rats showed a much lower response in corticosterone than the control animals. However, the response in ACTH to either stressor was comparable between groups. Thus, in exercising rats physically demanding stressors evoke enhanced glucocorticoid responses whereas mild psychologically stressful stimuli such as novelty result in an attenuated glucocorticoid response. Interestingly, this attenuated hormone response corresponded with the observation that the exercising rats showed less anxious behaviour in the novelty situation. Conclusions: The differential responses in plasma corticosterone levels to different types of stress in the face of comparable responses in ACTH levels underscore the existence of critical regulatory control mechanisms at the level of the adrenal gland. We have hypothesized that changes in the sympathoadrenomedullary input may play an important role in these distinct glucocorticoid responses to stress. Our previous studies have shown similar changes in voluntarily exercising mice. Therefore, we conclude that the effects of exercise on the organism are not species-specific. Thus, our observations may have translational implications for the human situation.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 82%

Voluntary Exercise Impacts on the Rat Hypothalamic-Pituitary-Adrenocortical Axis Mainly at the Adrenal Level

Droste

Chandramohan²,

Hill³

et al. 2007

Neuroendocrinology

131

143

View full text Add to dashboard Cite

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“…In fact, it has been suggested that this higher capacity to secrete A can be reflected by significantly higher A concentrations in endurance-trained athletes (Kjae¨r et al 1986;Kjae¨r and Galbo 1988). This may be explained by an increase of the adrenal medulla volume and an increase of the A content of these glands as reported in rats (Stallknecht et al 1990;Schmidt et al 1992). In our study, untrained subjects also exhibited the lowest NA max values.…”

Section: Catecholamine Responses To the Wingate Testsupporting

confidence: 70%

Effect of the intensity of training on catecholamine responses to supramaximal exercise in endurance-trained men

Jacob

Zouhal

Prioux

et al. 2004

European Journal of Applied Physiology

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In this study we investigated whether plasma catecholamine responses to the Wingate test are affected by the intensity of training in endurance-trained subjects. To do this we compared plasma adrenaline (A) and noradrenaline (NA) concentrations in response to a Wingate test in three different groups: specialist middledistance runners (MDR) in 800-m and 1,500-m races, specialist long-distance runners (LDR) 5,000-m and 10,000-m races, and untrained subjects (UT). The maximal power (W max ) and the mean power (W) were determined from the Wingate test. Blood lactate (La), plasma A and NA concentrations were analysed at rest (La 0 , A 0 and NA 0 ), immediately at the end of the exercise (A max and NA max ) and after 5 min recovery (La max , A 5 and NA 5 ). The ratio A max /NA max was considered as an index of the adrenal medulla responsiveness to the sympathetic nervous activity. At the end of the test, W max and W were similar in the three groups but La max was significantly greater in MDR compared to LDR and UT [15.2 (2.2) mmol l )1 , 11.7 (3.1) mmol l )1 , 11.6 (1.6) mmol l )1 , respectively, for MDR, LDR and UT; mean (SD)]. Concerning the plasma catecholamine concentrations in response to exercise, MDR and LDR A max values [3.73 (1.53) nmol l )1 , 3.47 (0.74) nmol l )1 , respectively, for MDR and LDR] were significantly greater than those of UT [1.48 (0.32) nmol l )1 ] who also exhibited the lowest NA max values [11.09 (6.58) nmol l )1 ] compared to MDR and LDR [20.43 (3.51) nmol l )1 ; 15.85 (4.88) nmol l )1 , respectively, for MDR and LDR]. However, no significant differences were observed between the two trained groups either for A max or NA max. These results suggest that long-term endurance training can enhance plasma catecholamine concentrations in response to supramaximal exercise. However, as there were no significant differences between MDR and LDR A max and NA max values, the effect of the intensity of training remains to be clarified.

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“…In a more recent study, the adrenal medulla volume, as well as the adrenal content of adrenaline, have been found to be larger/ higher in endurance trained young animals compared to control rats who were either weight matched, sham trained or cold stressed ( Fig. 4; Stallknecht et al 1990). …”

Section: Adrenal Medulla Volume and Adrenaline Content After Physicalmentioning

confidence: 84%

“…The training induced enlargement of the adrenal medulla was mainly a hypertrophy, and the increased adrenaline content was due to the enlargement of the gland rather than due to increased medullary adrenaline concentration (Stallknecht et al 1990;Schmidt et al 1992). Therefore, it is likely that in humans also the adrenal medulla adapts as a result of training, but that several years of training are required to advance this adaptation.…”

Section: Adrenal Medulla Volume and Adrenaline Content After Physicalmentioning

confidence: 99%

Adrenal medulla and exercise training

Kjær

1998

European Journal of Applied Physiology

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The adrenaline release from the adrenal medulla increases during exercise, but at a given absolute work intensity the magnitude of this response is less pronounced in endurance trained vs sedentary individuals most likely due to a lower sympathetic stimulation of the adrenal medulla. However, when trained and untrained subjects are compared at identical relative work loads as well as in response to numerous non-exercise stimuli. endurance trained athletes have a higher epinephrine secretion capacity compared to sedentary individuals. This indicates a development of a so-called "sports adrenal medulla" as a result of a long term adaptation of an endocrine gland to physical training. Such an adaptation is parallel to adaptations taking place in other tissues like skeletal muscle and the heart. and can be advantageous in relation to both exercise performance in the competing athlete and cause a biological rejuvenation in relation to aging.

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Diminished epinephrine response to hypoglycemia despite enlarged adrenal medulla in trained rats

Cited by 30 publications

References 0 publications

Voluntary Exercise Impacts on the Rat Hypothalamic-Pituitary-Adrenocortical Axis Mainly at the Adrenal Level

Voluntary Exercise Impacts on the Rat Hypothalamic-Pituitary-Adrenocortical Axis Mainly at the Adrenal Level

Effect of the intensity of training on catecholamine responses to supramaximal exercise in endurance-trained men

Adrenal medulla and exercise training

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