Orth D N, Nicholson W E
Endocrinology. 1982 Aug;111(2):559-63. doi: 10.1210/endo-111-2-559.
Equine Cushing's disease is caused by hypersecretion of ACTH by hyperplasia or adenomas of pars intermedia (PI) cells, in contrast to human Cushing's disease, which is caused by hyperplasia or adenomas of pars distalis (PD) ACTH-secreting cells. We assayed both bioactive and immunoreactive (IR) ACTH in two normal equine pituitary glands and in the PD, PI, and pars nervosa of four such glands, as well as in the PI adenomas of five horses with Cushing's disease. In normal horse pituitaries, as in those of other species, most of the bioactive and IR-ACTH was found in PD, much less in PI, and only traces in pars nervosa. In PI adenomas of horses with Cushing's disease, bioactive ACTH concentrations were similar to those in normal PI, but the total tumor content of bioactive ACTH exceeded that of normal whole pituitary. IR-ACTH concentrations were even higher in PI tumors, suggesting that some of the tumor ACTH was biologically inactive. Plasma IR-ACTH, which, like the PI adenoma tissue, presumably included a major fraction of bioactive ACTH, was greatly elevated in five horses with Cushing's disease and would account for the adrenal hyperplasia and hyperfunction observed in these animals.
马库兴氏病是由中间部（PI）细胞增生或腺瘤导致促肾上腺皮质激素（ACTH）分泌过多引起的，与之形成对比的是，人类库兴氏病是由远侧部（PD）分泌ACTH的细胞增生或腺瘤引起的。我们检测了两个正常马垂体以及四个此类垂体的PD、PI和神经部中生物活性ACTH和免疫反应性（IR）ACTH的含量，还检测了五匹患有库兴氏病马的PI腺瘤中这两种物质的含量。在正常马垂体中，与其他物种一样，大部分生物活性ACTH和IR-ACTH存在于PD中，PI中的含量少得多，神经部中仅有微量。在患有库兴氏病马的PI腺瘤中，生物活性ACTH浓度与正常PI中的相似，但生物活性ACTH的肿瘤总含量超过了正常整个垂体的含量。PI肿瘤中IR-ACTH浓度甚至更高，这表明部分肿瘤ACTH没有生物活性。血浆IR-ACTH，与PI腺瘤组织一样，可能包含大部分生物活性ACTH，在五匹患有库兴氏病的马中大幅升高，这可以解释这些动物中观察到的肾上腺增生和功能亢进。
