Shields P P, Dixon J E, Glembotski C C
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104.
J Biol Chem. 1988 Sep 5;263(25):12619-28.
Atrial natriuretic factor (ANF) is stored in mammalian atria primarily as ANF-(1-126), the precursor to the known circulating form of the hormone ANF-(99-126). When primary cultures of atrial myocytes were maintained in a complete serum-free medium, they contained and secreted an ANF-(1-126)-like peptide. The addition of dexamethasone to the culture medium, however, resulted in the secretion of a molecule with chromatographic characteristics identical to ANF-(99-126), although the intracellular storage form of ANF was unchanged. Radiosequencing and amino acid analysis confirmed that the cultures maintained in dexamethasone secreted authentic ANF-(99-126). Chronic exposure of the cells to dexamethasone also resulted in a significant increase in the quantity of immunoreactive ANF both contained and secreted by the cultures. Dexamethasone stimulated ANF processing and secretion by atrial cultures in a dose-dependent manner, with an approximate EC50 of 10 nM. This stimulation could be reversed by removing the glucocorticoid from the culture medium. ANF processing was also stimulated by the specific glucocorticoid receptor agonist RU 28362, and both DEX- and RU 28362-stimulated ANF processing was inhibited by the specific glucocorticoid receptor antagonist RU 38486. Ventricular cells, which possess few granules and release ANF in a constitutive fashion, were also capable of processing ANF in a glucocorticoid-dependent fashion. Medium freshly removed from atrial cultures did not convert ANF-(1-126) to ANF-(99-126) nor was exogenous ANF-(1-126) efficiently processed when added to the medium of actively processing cultures. These results indicate that the post-translational processing of ANF-(1-126) to ANF-(99-126) likely occurs within or in close association with the cardiac myocytes and is not dependent on the presence of large quantities of secretory granules. Furthermore, it is apparent that both the expression and the post-translational processing of ANF by cultured cardiac myocytes is specifically regulated by glucocorticoids.
心房利钠因子（ANF）在哺乳动物心房中主要以ANF-(1-126)的形式储存，它是激素ANF-(99-126)已知循环形式的前体。当心房肌细胞原代培养物维持在完全无血清培养基中时，它们含有并分泌一种ANF-(1-126)样肽。然而，向培养基中添加地塞米松会导致分泌出一种具有与ANF-(99-126)相同色谱特征的分子，尽管ANF的细胞内储存形式未改变。放射性测序和氨基酸分析证实，在地塞米松中培养的细胞分泌的是真实的ANF-(99-126)。细胞长期暴露于地塞米松还导致培养物中所含和分泌的免疫反应性ANF数量显著增加。地塞米松以剂量依赖的方式刺激心房培养物中ANF的加工和分泌，其近似EC50为10 nM。通过从培养基中去除糖皮质激素可以逆转这种刺激。特异性糖皮质激素受体激动剂RU 28362也刺激ANF加工，并且地塞米松和RU 28362刺激的ANF加工均被特异性糖皮质激素受体拮抗剂RU 38486抑制。心室细胞含有很少的颗粒并以组成性方式释放ANF，它们也能够以糖皮质激素依赖的方式加工ANF。刚从心房培养物中取出的培养基不会将ANF-(1-126)转化为ANF-(99-126)，当添加到正在进行有效加工的培养物的培养基中外源ANF-(1-126)也不能被有效加工。这些结果表明，ANF-(1-126)向ANF-(99-126)的翻译后加工可能发生在心肌细胞内或与心肌细胞紧密相关处，并且不依赖于大量分泌颗粒的存在。此外，很明显，培养的心肌细胞中ANF的表达和翻译后加工均受到糖皮质激素的特异性调节。
