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Adrenaline and glycogenolysis in skeletal muscle during exercise: a study in adrenalectomised humans
Ist Teil von
The Journal of physiology, 2000-10, Vol.528 (2), p.371-378
Ort / Verlag
Oxford, UK: The Physiological Society
Erscheinungsjahr
2000
Quelle
Wiley Blackwell Single Titles
Beschreibungen/Notizen
The role of adrenaline in regulating muscle glycogenolysis and hormone-sensitive lipase (HSL) activity during exercise was
examined in six adrenaline-deficient bilaterally adrenalectomised, adrenocortico-hormonal-substituted humans (Adr) and in
six healthy control individuals (Con).
Subjects cycled for 45 min at â¼70 % maximal pulmonary O 2 uptake ( VÌ O 2 ,max ) followed by 15 min at â¼86 % VÌ O 2 ,max either without (âAdr and Con) or with (+Adr) adrenaline infusion that elevated plasma adrenaline levels (45 min, 4.49 ± 0.69
nmol l â1 ; 60 min, 12.41 ± 1.80 nmol l â1 ). Muscle samples were obtained at 0, 45 and 60 min of exercise.
In âAdr and Con, muscle glycogen was similar at rest (âAdr, 409 ± 19 mmol (kg dry wt) â1 ; Con, 453 ± 24 mmol (kg dry wt) â1 ) and following exercise (âAdr, 237 ± 52 mmol (kg dry wt) â1 ; Con, 227 ± 50 mmol (kg dry wt) â1 ). Muscle lactate, glucose-6-phosphate and glucose were similar in âAdr and Con, whereas glycogen phosphorylase ( a/a + b à 100%) and HSL (% phosphorylated) activities increased during exercise in Con only. Adrenaline infusion increased activities
of phosphorylase and HSL as well as blood lactate concentrations compared with those in âAdr, but did not enhance glycogen
breakdown (+Adr, glycogen following exercise: 274 ± 55 mmol (kg dry wt) â1 ) in contracting muscle.
The present findings demonstrate that during exercise muscle glycogenolysis can occur in the absence of adrenaline, and that
adrenaline does not enhance muscle glycogenolysis in exercising adrenalectomised subjects. Although adrenaline increases the
glycogen phosphorylase activity it is not essential for glycogen breakdown in contracting muscle. Finally, a novel finding
is that the activity of HSL in human muscle is increased in exercising man and this is due, at least partly, to stimulation
by adrenaline.