Mol J A, Selman P J, Sprang E P, van Neck J W, Oosterlaken-Dijksterhuis M A
Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht, The Netherlands.
J Reprod Fertil Suppl. 1997;51:339-44.
The growth hormone (GH) and insulin-like growth factor (IGF) system is an important regulatory system of mammalian epithelial cell proliferation and differentiation. The biological effects of the IGFs are modulated by six different binding proteins (IGFBPs). Progestins play an important role in the regulation of the dynamics of mammary gland development and involution through the modulation of these growth regulating factors. In dogs and cats, progestins stimulate the local production of GH in the mammary gland. In dogs, this results in high plasma concentrations of GH and a concomitant increase in plasma IGF-I and IGFBP-3 concentrations. The administration of progestins also induces high plasma concentrations of IGF-II, even before GH concentrations start to increase. In the mammary gland of the normal bitch, IGFBP-5 and IGFBP-2 are the main IGFBPs expressed. Progestin administration results in a decrease of mRNA encoding IGFBP-5, but does not alter the concentration of mRNA encoding IGFBP-2. This local mammary system of GH, IGFs and IGFBPs plays an important role in the regulation of mammogenesis, lactation and involution. However, the presence of a high proliferative environment may also enhance the risk of malignant transformation and promotion of tumour growth with an associated inhibition of programmed cell death.
生长激素（GH）和胰岛素样生长因子（IGF）系统是哺乳动物上皮细胞增殖和分化的重要调节系统。IGF的生物学效应由六种不同的结合蛋白（IGFBP）调节。孕激素通过调节这些生长调节因子，在乳腺发育和退化的动态调节中发挥重要作用。在犬和猫中，孕激素刺激乳腺中GH的局部产生。在犬中，这导致血浆中GH浓度升高，同时血浆IGF-I和IGFBP-3浓度增加。即使在GH浓度开始升高之前，孕激素的给药也会诱导血浆中IGF-II浓度升高。在正常母犬的乳腺中，IGFBP-5和IGFBP-2是主要表达的IGFBP。孕激素给药导致编码IGFBP-5的mRNA减少，但不改变编码IGFBP-2的mRNA浓度。这种局部的乳腺GH、IGF和IGFBP系统在乳腺发生、泌乳和退化的调节中起重要作用。然而，高增殖环境的存在也可能增加恶性转化和肿瘤生长促进的风险，并伴有程序性细胞死亡的抑制。
