Field M, Sheerin H E, Henderson A, Smith P L
Am J Physiol. 1975 Jul;229(1):86-92. doi: 10.1152/ajplegacy.1975.229.1.86.
Effects of catecholamines on cyclic AMP (cAMP) levels and ion fluxes were examined in isolated rabbit ileal mucosa. The base-line cAMP level was unaffected by epinephrine (Epi), norepinephrine (Norepi), and isoproterenol. The theophylline-augmented cAMP level was decreased slightly be Epi in one series of experiments but not in another. Propranolol did not enhance this effect. The increase in cAMP level produced by cholera toxin was almost completely reversed by addition of Epi or Norepi. This reversal was prevented by phenoxybenzamine. Epi also partially reversed the increase in cAMP level produced by prostaglandin E1. Effects of Epi on ion fluxes were determined following addition of secretagogues. Epi significantly decreased theophylline-induced but not cAMP or cholera toxin-induced Cl secretion. A decrease in short-circuit current was nonetheless observed in the latter two instances. The observed discrepancies between alpha-adrenergic effects on cAMP levels and ion fluxes suggest the following possibilities: 1) ion transport-related cAMP is only a small fraction of total mucosal cAMP; 2) cAMP-induced active ion secretion is only slowly reversible, or 3) effects of alpha-adrenergic stimuli on ion transport are not due to inhibition of cAMP accumulation.
在离体兔回肠黏膜中研究了儿茶酚胺对环磷酸腺苷（cAMP）水平和离子通量的影响。基线cAMP水平不受肾上腺素（Epi）、去甲肾上腺素（Norepi）和异丙肾上腺素的影响。在一系列实验中，茶碱增强的cAMP水平在Epi作用下略有下降，但在另一系列实验中未出现这种情况。普萘洛尔并未增强这种作用。添加Epi或Norepi后，霍乱毒素引起的cAMP水平升高几乎完全逆转。苯氧苄胺可阻止这种逆转。Epi还部分逆转了前列腺素E1引起的cAMP水平升高。在添加促分泌剂后测定Epi对离子通量的影响。Epi显著降低了茶碱诱导的Cl分泌，但对cAMP或霍乱毒素诱导的Cl分泌无影响。然而，在后两种情况下观察到短路电流降低。α-肾上腺素能对cAMP水平和离子通量的影响之间存在差异，提示以下几种可能性：1）与离子转运相关的cAMP只是黏膜总cAMP的一小部分；2）cAMP诱导下的主动离子分泌只是缓慢可逆的；或者3）α-肾上腺素能刺激对离子转运的影响并非由于抑制cAMP积累。
