Craven T G, Kem D C, Schiebinger R J
Department of Medicine, University of Oklahoma Health Science Center, Oklahoma City.
Endocrinology. 1988 Mar;122(3):826-30. doi: 10.1210/endo-122-3-826.
Previous studies have shown that atrial natriuretic peptides (ANPs) inhibit the secretion of aldosterone by isolated rat adrenal glomerulosa cells stimulated by angiotensin II, ACTH, and potassium. Structure-function studies have concentrated on the significance of the C- and N-terminal chains for the biological activity of the peptide. We investigated the role of phenylalanine at positions 8 and 26 by using [Ala8]human (h) ANP or [Ala26]hANP analogs to inhibit potassium-stimulated aldosterone secretion in granulosa cells. hANP-(1-28) inhibited potassium-stimulated aldosterone secretion with an IC50 of 0.48 nM. Synthetic [Ala26]hANP inhibited the aldosterone response to potassium with an inhibitory curve relative to hANP-(1-28) (rIC50) of 6.0 nM, which was significantly greater than that for hANP (P less than 0.001). Synthetic [Ala8]hANP was markedly less effective as an inhibitor, with an estimated rIC50 of 3.0 microM (P less than 0.0001). To determine whether the analogs act as competitive antagonists to hANP-(1-28), experiments were performed in which a fixed concentration (0.1 microM) of the analog was incubated in the presence of increasing concentrations of hANP-(1-28). When hANP-(1-28) was incubated with [Ala8]hANP, the rIC50 (0.2 nM) was significantly less than that for hANP-(1-28) alone (P less than 0.02). When hANP-(1-28) was incubated with [Ala26]hANP, the rIC50 was 0.1 nM. In summary, [Ala8]hANP and [Ala26]hANP were significantly less potent than hANP-(1-28) as inhibitors of aldosterone production from granulosa cells. Both analogs shifted the hANP-(1-28) dose-response curve to the left. Neither analog functioned as a competitive antagonist to hANP-(1-28). Our results indicate that the hydrophobic phenyl groups at these two positions are required for full biological potency of ANP as an inhibitor of aldosterone production.
先前的研究表明，心房利钠肽（ANP）可抑制由血管紧张素II、促肾上腺皮质激素（ACTH）和钾刺激的离体大鼠肾上腺球状带细胞分泌醛固酮。结构-功能研究主要集中在C端和N端链对该肽生物活性的意义。我们通过使用[Ala8]人（h）ANP或[Ala26]hANP类似物来抑制球状带细胞中钾刺激的醛固酮分泌，研究了第8位和第26位苯丙氨酸的作用。hANP-(1-28)抑制钾刺激的醛固酮分泌，IC50为0.48 nM。合成的[Ala26]hANP抑制醛固酮对钾的反应，相对于hANP-(1-28)的抑制曲线（rIC50）为6.0 nM，显著高于hANP（P<0.001）。合成的[Ala8]hANP作为抑制剂的效果明显较差，估计rIC50为3.0 μM（P<0.0001）。为了确定这些类似物是否作为hANP-(1-28)的竞争性拮抗剂起作用，进行了实验，即在固定浓度（0.1 μM）的类似物存在下，加入浓度不断增加的hANP-(1-28)进行孵育。当hANP-(1-28)与[Ala8]hANP一起孵育时，rIC50（0.2 nM）显著低于单独的hANP-(1-28)（P<0.02）。当hANP-(1-28)与[Ala26]hANP一起孵育时，rIC50为0.1 nM。总之，作为球状带细胞醛固酮产生的抑制剂，[Ala8]hANP和[Ala26]hANP的效力明显低于hANP-(1-28)。两种类似物均使hANP-(1-28)的剂量反应曲线向左移动。两种类似物均不作为hANP-(1-28)的竞争性拮抗剂起作用。我们的结果表明，这两个位置的疏水苯基对于ANP作为醛固酮产生抑制剂的完全生物活性是必需的。
