Expression and localization of intestine-derived faty acid-binding proteins in the rat

脂肪酸结合蛋白(FABP)是在哺乳动物组织中表达的一种同源、低分子量的胞浆蛋白家族，对脂肪酸化有很高的亲和力。已知大鼠小肠表达多种不同的FABP，包括新发现的肠道15 kDa蛋白(1-15p)。我们用免疫细胞化学和原位杂交技术研究了I-15P在大鼠全身的表达和定位。两种技术都证明了I-15P在回肠的肠细胞、卵巢的黄体细胞和肾上腺的类固醇内分泌细胞亚群中都有表达。免疫电子显微镜进一步证明，I-15P定位于上述细胞的胞浆和核基质区域。这些结果表明，I-15P不仅在回肠上皮对胆盐的转运中起作用，而且在某些类固醇激素的代谢中也起作用。其次，研究了两种FABP的免疫组织化学定位，即I-15P和心脏FABP(H-FABP)在发育期和促性腺激素诱导排卵的大鼠卵巢中的分布。在卵巢的出生后发育过程中，I-15p免疫反应从2周到4周暂时性地定位于一小部分膜/间质细胞，然后从5周开始定位于黄体细胞，与周期的开始相一致，一直持续到成年。在孕马血清促性腺激素和人绒毛膜促性腺激素诱导的未成熟(3周龄)卵巢中，I-15P免疫反应首先出现在大的排卵前卵泡的黄体化颗粒细胞中。相反，H-FABP免疫反应在最初的2周内暂时出现在卵泡上皮(颗粒)细胞中，之后在产后2周至成年期的膜/间质细胞中出现。这些结果表明，两种类型的FABP在大鼠卵巢不同的类固醇细胞群中表达，这意味着

A family of homologous, low-molecular-weight cytosolic proteins with high affinity for fatty acidsis expressed in mammalian tissues and called fatty acid-binding protein (FABP). Rat small intestine is knownto express several distinct FABPs, including newly-discovered intestinal 15 kDa protein (1-15P). We studied the expresion and localization of I-15P in the entire rat body, using the immunocytochemistry to localize protein and in situ hybridization to localize mRNA.Both techniques demonstrated the expression of I-15P in the enterocytes of ileum, luteal cells of ovary and a subpopulation of steroid-endocrine cells of adrenal gland. Immuno-electron microscopy further demonstrated that I-15P is localized in both the cytoplasmic and nuclear matrix regions of above cells. These results suggested the roles of I-15P not only in the transport of bile salts by ileal epithelium but also in the metabolisms of certain steroid hormones. Next, the immuohistohemical localizations of two types of FABPs, i.e., I-15P and heart FABP (H-FABP), were examined in the developing rat overies and in the rat overies induced to ovulate by gonadotropins. In the postnatal development of ovary, I-15P-immunoreactivity was localized temporarilyin a small subpopulation of theca/interstitial cells from 2 weeks to 4 weeks and then in the luteal cells from 5 weeks, in coincidence with the onset of cycles, into adulthood. In the immature (3 week old) ovaries inducedto ovulate by treatment with pregnant mare serum gonadotropin and human chorionic gonadotropin, I-15P-immunoreactivity first appeard in the luteinizing granulosa cells of large preovulatory follicles. In contrast, H-FABP-immunoreactivity was present temporarily in the follicular epithelial (granulosa) cells during the initial 2 weeks and thereafter in the theca/interstitial cells from 2 weeks postpartum into adulthood. These results suggested that two types of FABPs are expressed in distinct steroid cell populations of rat ovary, implecatin