Ikeda U, Kanbe T, Kawahara Y, Yokoyama M, Shimada K
Department of Cardiology, Jichi Medical School, Tochigi, Japan.
Circulation. 1996 Nov 15;94(10):2560-5. doi: 10.1161/01.cir.94.10.2560.
Plasma levels of adrenomedullin are increased in patients with congestive heart failure, but there has been no report concerning the effects of adrenomedullin on the heart. We investigated the effects of adrenomedullin on NO synthase activity in cardiac myocytes.
We measured the production of nitrite, a stable metabolite of NO, in cultured neonatal rat cardiac myocytes with the Griess reagent. Inducible NO synthase mRNA and protein expression were assayed by Northern and Western blotting, respectively. Incubation of the cultures with interleukin-1 beta (10 ng/mL) for 24 hours caused a significant increase in nitrite accumulation. Adrenomedullin significantly augmented nitrite production by interleukin-1 beta-stimulated but not by unstimulated cardiac myocytes in a dose-dependent manner (10(-10) to 10(-6) mol/L). The adrenomedullin-induced nitrite production by interleukin-1 beta-stimulated cells was accompanied by increased inducible NO synthase mRNA and protein expression. In the presence of dibutyryl cAMP, the interleukin-1 beta-induced nitrite accumulation was increased further, but the stimulatory effect of adrenomedullin on nitrite production was abolished. Adrenomedullin dose-dependently increased intracellular cAMP levels in cardiac myocytes. Addition of the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP[8-37] to the culture dose-dependently inhibited both cAMP and NO generation stimulated by adrenomedullin.
These results indicate that adrenomedullin acts on cardiac myocytes and augments NO synthesis in these cells under cytokine-stimulated conditions, at least partially through a cAMP-dependent pathway.
充血性心力衰竭患者血浆肾上腺髓质素水平升高，但尚无关于肾上腺髓质素对心脏影响的报道。我们研究了肾上腺髓质素对心肌细胞中一氧化氮合酶活性的影响。
我们用格里斯试剂测量培养的新生大鼠心肌细胞中一氧化氮的稳定代谢产物亚硝酸盐的生成量。分别通过Northern印迹法和Western印迹法检测诱导型一氧化氮合酶mRNA和蛋白表达。用白细胞介素-1β（10 ng/mL）孵育培养物24小时导致亚硝酸盐积累显著增加。肾上腺髓质素以剂量依赖方式（10^(-10)至10^(-6) mol/L）显著增强白细胞介素-1β刺激的而非未刺激的心肌细胞的亚硝酸盐生成。白细胞介素-1β刺激的细胞中肾上腺髓质素诱导的亚硝酸盐生成伴随着诱导型一氧化氮合酶mRNA和蛋白表达增加。在存在二丁酰环磷腺苷（dibutyryl cAMP）的情况下，白细胞介素-1β诱导的亚硝酸盐积累进一步增加，但肾上腺髓质素对亚硝酸盐生成的刺激作用被消除。肾上腺髓质素剂量依赖性增加心肌细胞内cAMP水平。向培养物中添加降钙素基因相关肽（CGRP）受体拮抗剂CGRP[8-37]剂量依赖性抑制肾上腺髓质素刺激的cAMP和一氧化氮生成。
这些结果表明，肾上腺髓质素作用于心肌细胞，并在细胞因子刺激条件下至少部分通过cAMP依赖性途径增强这些细胞中的一氧化氮合成。
