Chang P I, Rutlen D L
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
Am J Physiol. 1991 Nov;261(5 Pt 2):H1499-507. doi: 10.1152/ajpheart.1991.261.5.H1499.
The effect of beta-adrenergic agonists on splanchnic intravascular volume (SIV), measured with radionuclide imaging, and the subsequent influence of such volume changes on cardiac output (CO) were examined in 40 anesthetized dogs. Isoproterenol (6 micrograms/min) caused a decrease in total SIV of 12 +/- 1% (P less than 0.001). The decrease was due entirely to a decrease in splenic volume of 24 +/- 3% (P less than 0.001), since volume increased in the remainder of the splanchnic vasculature [hepatic and mesenteric volume increased 12 +/- 2% (P less than 0.001) and 11 +/- 3% (P less than 0.02), respectively]. CO increased from 1,724 +/- 187 to 3,138 +/- 321 ml/min (P less than 0.001); after subsequent splenectomy, isoproterenol caused a similar increment. Isoproterenol-associated SIV changes were not altered by carotid denervation and vagotomy or by beta 1-adrenergic inhibition with metoprolol but were abolished by nonselective beta-adrenergic inhibition with propranolol. With a larger dose of metoprolol and smaller dose of isoproterenol to minimize beta 1-adrenergic effects, the isoproterenol-associated CO increment was attenuated (P less than 0.01) by splenectomy. With the beta 2-agonist terbutaline (41 micrograms/min) after metoprolol, total SIV decreased 15 +/- 4% (P less than 0.001). After subsequent alpha-adrenergic inhibition with phenoxybenzamine, terbutaline caused no change in SIV and an attenuated (P less than 0.05) increase in CO. Thus beta-adrenergic agonist administration causes a decrease in total SIV due entirely to a decrease in splenic volume. The SIV decrement is dependent on beta 2- and alpha-adrenoceptor stimulation and appears to enhance CO only if beta 1-adrenergic effects are minimized.
在40只麻醉犬中，研究了β-肾上腺素能激动剂对放射性核素成像测量的内脏血管内血容量（SIV）的影响，以及这种血容量变化对心输出量（CO）的后续影响。异丙肾上腺素（6微克/分钟）使总SIV降低了12±1%（P<0.001）。这种降低完全是由于脾脏体积减少了24±3%（P<0.001），因为内脏血管系统其余部分的体积增加了[肝脏和肠系膜体积分别增加了12±2%（P<0.001）和11±3%（P<0.02）]。CO从1724±187毫升/分钟增加到3138±321毫升/分钟（P<0.001）；随后进行脾切除术后，异丙肾上腺素引起了类似的增加。与异丙肾上腺素相关的SIV变化不受颈动脉去神经支配和迷走神经切断术的影响，也不受美托洛尔对β1-肾上腺素能的抑制作用影响，但被普萘洛尔的非选择性β-肾上腺素能抑制作用消除。使用较大剂量的美托洛尔和较小剂量的异丙肾上腺素以最小化β1-肾上腺素能效应时，脾切除术后异丙肾上腺素相关的CO增加减弱（P<0.01）。在美托洛尔之后使用β2-激动剂特布他林（41微克/分钟），总SIV降低了15±4%（P<0.001）。在用酚苄明进行α-肾上腺素能抑制后，特布他林对SIV无影响，CO增加减弱（P<0.05）。因此，给予β-肾上腺素能激动剂会导致总SIV降低，这完全是由于脾脏体积减少所致。SIV的减少依赖于β2-和α-肾上腺素能受体的刺激，并且似乎只有在β1-肾上腺素能效应最小化时才会增强CO。
