Holmes W N, Cronshaw J
J Exp Zool. 1984 Dec;232(3):627-31. doi: 10.1002/jez.1402320331.
There are two regions of steroidogenic tissue in the bird adrenal gland: a subcapsular zone (SCZ) 40-60 cells thick consisting of cells with irregularly shaped nuclei, relatively little smooth endoplasmic reticulum, and mitochondria with shelflike cristae that surrounds an inner zone (IZ) of tissue comprised of smaller cells with rounded nuclei, a more abundant endoplasmic reticulum, and mitochondria with tubular cristae. The cristae in the mitochondria of IZ cells, but not the SCZ cells, seem to be quite labile and only assume the tubular configuration when subjected to corticotropic stimulation. The properties of the steroidogenic cells in the two zones are quantitatively distinct, the cells of the SCZ producing relatively more aldosterone and relatively less corticosterone than the cells of the IZ. The corticotropic responsiveness of the IZ cells is dependent on the synthesis of protein in the cytoplasm and a normal pattern of microfilament assembly. The dose responsiveness of both the IZ and the SCZ cells in vitro is a complex quadratic function of the corticotropin concentration to which they are exposed; the semilogarithmic linear response to corticotropin is restricted to a narrow midrange of concentrations, and at high concentrations cells from both zones of the gland respond submaximally. Throughout the dose-response range, however, the steroidogenic cells of the IZ are more sensitive and more responsive to corticotropic stimulation than are the cells of the SCZ.
一个是被膜下区（SCZ），厚40 - 60个细胞，由细胞核形状不规则、滑面内质网相对较少以及具有板层状嵴的线粒体的细胞组成，该区域围绕着一个内部区域（IZ），IZ由细胞核圆形、内质网更丰富以及具有管状嵴的线粒体的较小细胞组成。IZ细胞线粒体中的嵴，而不是SCZ细胞线粒体中的嵴，似乎相当不稳定，只有在受到促肾上腺皮质激素刺激时才呈现管状结构。两个区域中类固醇生成细胞的特性在数量上有所不同，SCZ细胞产生的醛固酮相对较多，皮质酮相对较少，而IZ细胞则相反。IZ细胞对促肾上腺皮质激素的反应性取决于细胞质中蛋白质的合成和微丝组装的正常模式。体外IZ细胞和SCZ细胞的剂量反应性是它们所接触的促肾上腺皮质激素浓度的复杂二次函数；对促肾上腺皮质激素的半对数线性反应仅限于较窄的浓度范围，在高浓度时，来自肾上腺两个区域的细胞反应都未达到最大值。然而，在整个剂量反应范围内，IZ的类固醇生成细胞比SCZ的细胞对促肾上腺皮质激素刺激更敏感、反应更强烈。
