Genovese A, Levi R
Prog Clin Biol Res. 1987;230:345-60.
The inotropic effect of histamine on the human myocardium consists of two opposing components: positive, H2-mediated, and negative, H1-mediated. Because adenosine is known to antagonize histamine H2-responses, we assessed whether adenosine may unmask H1-mediated histamine responses in human myocardium. We found that adenosine modulates the stimulatory effects of histamine on pectinate muscles isolated from human right atrium and converts them as a function of its concentration from positive to negative. Further, histamine potentiated the tendency of adenosine to induce cardiac arrest. The H1-blocker pyrilamine antagonized the adenosine-induced suppression of the positive inotropic and chronotropic effects of histamine. Thus, our data indicate that the negative inotropic and chronotropic effects of histamine in the presence of adenosine result in part from an antagonism of H2-mediated increases in rate and contractility, and in part from an unmasking of H1-mediated decreases in the same parameters. Adenosine and histamine may be co-released in response to hypoxia or ischemia. In spite of the protection that adenosine may afford the human myocardium against excessive histamine stimulation, adenosine may also unmask the inhibitory actions of histamine, promoting dysrhythmia, and negative inotropic and chronotropic effects.
由H2介导的正向作用和由H1介导的负向作用。由于已知腺苷可拮抗组胺的H2反应，我们评估了腺苷是否可能揭示人心肌中H1介导的组胺反应。我们发现，腺苷可调节组胺对从人右心房分离出的梳状肌的刺激作用，并根据其浓度将其从正向作用转变为负向作用。此外，组胺增强了腺苷诱导心脏骤停的倾向。H1阻滞剂吡苄明可拮抗腺苷诱导的组胺正向变力和变时作用的抑制。因此，我们的数据表明，在存在腺苷的情况下，组胺的负向变力和变时作用部分源于对H2介导的心率和收缩力增加的拮抗，部分源于H1介导的相同参数降低的暴露。腺苷和组胺可能会在缺氧或缺血时共同释放。尽管腺苷可能为人心肌提供保护，使其免受过度组胺刺激，但腺苷也可能揭示组胺的抑制作用，促进心律失常以及负向变力和变时作用。
