Involvement of muscarinic cholinergic and alpha2-adrenergic mechanisms in growth hormone secretion during exercise in humans.
The purpose of this study was to examine the role of muscarinic cholinergic and alpha2-adrenergic mechanisms in growth hormone (GH) secretion during exercise in humans. The GH responses induced during moderate-intensity exercise (using a cycle ergometer at 60% maximal oxygen uptake, VO2max, for 30 min) without treatment (control) and after the administration of a muscarinic cholinergic antagonist (atropine 1 mg) or after an alpha2-adrenergic antagonist (yohimbine 15 mg) were compared in seven healthy men. Although, serum GH concentration had increased significantly after exercise in the control experiment [mean peak GH concentration 52.64 (SEM 18.60) ng x ml(-1)], the increase was suppressed by the administration of either atropine [mean peak GH concentration 8.64 (SEM 7.47) ng x ml(-1)] or yohimbine [mean peak GH concentration 17.50 (SEM 7.89) ng x ml(-1)]. The area under the curve of serum GH concentration against time was significantly lower in the experiment using these drugs [with atropine, mean area 458 (SEM 409) ng x ml(-1) min], with yohimbine mean area 946 (SEM 435) ng x ml(-1) min] than in the control experiment [mean area 3135 (SEM 1098) ng x ml(-1) x min]. These results suggest that muscarinic cholinergic and alpha2-adrenergic mechanisms are involved in GH secretion during exercise in humans.
Harada
T
T
Laboratory for Exercise Physiology, Chukyo University, Toyota, Aichi, Japan. tharada@cnc.chukyo-u.ac.jp
Yamauchi
T
T
Tsukanaka
A
A
Matsumura
Y
Y
Kurono
M
M
Honda
A
A
Matsui
N
N
D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000328:Adult; D019540:Area Under Curve; D001285:Atropine / Q000494:pharmacology*; D004837:Epinephrine / Q000097:blood; D015444:Exercise; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009638:Norepinephrine / Q000097:blood; D005082:Physical Exertion; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology; D011976:Receptors, Muscarinic / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology*
D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D018727:Muscarinic Antagonists; D018341:Receptors, Adrenergic, alpha-2; D011976:Receptors, Muscarinic; D019382:Human Growth Hormone; D015016:Yohimbine; D001285:Atropine; D009638:Norepinephrine; D004837:Epinephrine