Clancy R L, Moue Y, Erwig L P, Smith P G, Gonzalez N C
Department of Physiology, University of Kansas Medical Center, Kansas City 66160-7401, USA.
Respir Physiol. 1997 Jan;107(1):75-84. doi: 10.1016/s0034-5687(96)02502-9.
To role of beta-adrenergic and muscarinic cholinergic systems on maximal treadmill exercise performance and systemic O2 transport during hypoxic exercise (PIO2 approximately 70 Torr) was studied in rats acclimatized to hypobaric hypoxia (PIO2 approximately 70 Torr for 3 weeks, A rats) and in non-acclimatized littermates (NA rats). Untreated A rats had lower resting (fH) and maximal heart rate (fHmax) and cardiac output (Q), and higher maximal O2 uptake (VO2max) than NA. The only effect of cholinergic receptor blockade with atropine (Atp) was an increase in pre-exercise fH to comparable levels in A and in NA. beta 1-adrenergic receptor blockade with atenolol (Aten) lowered pre-exercise fH and (fHmax) to comparable values in A and in NA rats. However, since both pre-exercise fH and fHmax were lower in untreated A, the effect of Aten was relatively smaller in A. Aten reduced maximal exercise cardiac output (Qmax) in NA; however, tissue O2 extraction increased such that VO2max was not affected. Aten did not influence Qmax or any other parameter of systemic O2 transport in A. In conclusion the increased cholinergic tone may be responsible for the lower resting fH but not the lower fHmax of A; the integrity of the beta-adrenergic system is not necessary to attain VO2max in hypoxia either in A or in NA; the decreased response to beta-adrenergic stimulation in A limits the efficacy of this system on the mechanisms of systemic O2 transport and reduces the effect of its blockade on these mechanisms.
研究了β-肾上腺素能和毒蕈碱胆碱能系统对低压缺氧适应大鼠（A组大鼠，在PIO2约70托的环境中适应3周）和未适应的同窝幼鼠（NA组大鼠）在低氧运动（PIO2约70托）期间最大跑步机运动表现和全身氧气运输的作用。未处理的A组大鼠静息心率（fH）、最大心率（fHmax）和心输出量（Q）较低，而最大摄氧量（VO2max）高于NA组。用阿托品（Atp）阻断胆碱能受体的唯一作用是使运动前fH增加至A组和NA组的可比水平。用阿替洛尔（Aten）阻断β1-肾上腺素能受体可使运动前fH和（fHmax）降低至A组和NA组大鼠的可比值。然而，由于未处理的A组运动前fH和fHmax均较低，Aten在A组的作用相对较小。Aten降低了NA组最大运动心输出量（Qmax）；然而，组织氧摄取增加，使得VO2max不受影响。Aten对A组的Qmax或全身氧气运输的任何其他参数均无影响。总之，胆碱能张力增加可能是A组大鼠静息fH较低的原因，但不是fHmax较低的原因；无论是A组还是NA组，在低氧状态下达到VO2max并不需要β-肾上腺素能系统完整；A组对β-肾上腺素能刺激反应降低限制了该系统对全身氧气运输机制的功效，并降低了其阻断对这些机制的影响。
