肾上腺素和α-激动剂对兔胸膜腔液体吸收净速率的影响。

Zocchi L, Raffaini A, Agostoni E

Istituto di Fisiologia Umano I, Università di Milano, Italy.

Exp Physiol. 1997 May;82(3):507-20. doi: 10.1113/expphysiol.1997.sp004043.

Indirect evidence supporting a solute-coupled liquid absorption from the pleural space of rabbits has recently been provided; moreover, the beta 2-adrenoceptor agonist terbutaline has been found to increase this absorption. In this study the effect of adrenaline and alpha-adrenoceptor agonists on net rate of liquid absorption (Jnet) from albumin Ringer hydrothoraces of various sizes has been determined in anaesthetized rabbits. In hydrothoraces with adrenaline (5 x 10(-6) M) the relationship between Jnet and volume of liquid injected was displaced upwards by 0.09 ml h-1 relative to that in control hydrothoraces (P < 0.01). This displacement did not occur with lower adrenaline concentrations or after pretreatment with the beta-blocker propranolol. Hence, this increase in Jnet is mediated by stimulation of beta-receptors. It seems to be caused by an increase in solute-coupled liquid absorption, since beta-agonists inhibit lymphatic activity while, at relatively high concentrations, they may increase active transport. Conversely, the strong stimulation of lymphatic alpha-receptors that should occur with adrenaline after beta-blockade may fail to increase lymphatic drainage, because it has been shown that the increase in contraction frequency of lymphatics may be balanced by the decrease in their stroke volume. Arterial blood pressure during the hydrothoraces with adrenaline was unchanged. In hydrothoraces with the alpha 2-agonist clonidine (5 x 10(-6) M; a less potent agent than adrenaline) the slope of the relationship between Jnet and volume injected increased by 26% (P < 0.01), while its origin did not change. This increase in slope did not occur with a lower clonidine concentration or after pretreatment with the alpha-blocker phentolamine. Hence, it is caused by stimulation of alpha 2-receptors, which probably lead to an increase in lymphatic drainage related to liquid load. In hydrothoraces with the alpha 1-agonist phenylephrine (5 x 10(-6) or 10(-7) M) Jnet was simlar to control values.

最近有间接证据支持兔胸膜腔存在溶质偶联的液体吸收；此外，已发现β2肾上腺素能受体激动剂特布他林可增加这种吸收。在本研究中，已测定了肾上腺素和α肾上腺素能受体激动剂对麻醉兔不同大小白蛋白林格氏液胸腔内液体净吸收率（Jnet）的影响。在含有肾上腺素（5×10⁻⁶ M）的胸腔中，Jnet与注入液体体积之间的关系相对于对照胸腔向上偏移了0.09 ml/h（P<0.01）。较低浓度的肾上腺素或用β受体阻滞剂普萘洛尔预处理后未出现这种偏移。因此，Jnet的这种增加是由β受体的刺激介导的。这似乎是由于溶质偶联的液体吸收增加所致，因为β激动剂会抑制淋巴活动，而在相对高浓度时，它们可能会增加主动转运。相反，β受体阻滞剂后肾上腺素对淋巴α受体的强烈刺激可能无法增加淋巴引流，因为已表明淋巴管收缩频率的增加可能会被其每搏量的减少所平衡。注入肾上腺素时的动脉血压未发生变化。在含有α2激动剂可乐定（5×10⁻⁶ M；一种比肾上腺素效力弱的药物）的胸腔中，Jnet与注入体积之间关系的斜率增加了26%（P<0.01），而其起始点未改变。较低浓度的可乐定或用α受体阻滞剂酚妥拉明预处理后未出现这种斜率增加。因此，这是由α2受体的刺激引起的，这可能导致与液体负荷相关的淋巴引流增加。在含有α1激动剂去氧肾上腺素（5×10⁻⁶或10⁻⁷ M）的胸腔中，Jnet与对照值相似。