Smith Sean M, Vaughan Joan M, Donaldson Cynthia J, Fernandez Rosette E, Li Chien, Chen Alon, Vale Wylie W
Clayton Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.
Endocrinology. 2006 Mar;147(3):1213-23. doi: 10.1210/en.2005-1392. Epub 2005 Dec 8.
Cocaine- and amphetamine-regulated transcript (CART) is a highly expressed peptide implicated in the regulation of feeding, reward and reinforcement, and stress-related behaviors. CART has been localized to discrete cell populations in the brain, gut, adrenal gland, and pancreas. In contrast, CART-producing cell types in the pituitary gland remain ill defined. In the present study, double-label immunohistochemistry, employing a high-affinity antiserum we generated against CART-(62-102), was used to identify CART-producing cells in the pituitary gland. In the anterior pituitary, the majority of CART immunoreactivity (-ir) was localized in lactotropes; minor populations of CART-ir cells were identified as somatotropes and corticotropes. In the posterior pituitary, CART-ir extensively colocalized with oxytocin-containing fibers; in contrast, only a few vasopressin fibers contained CART-ir. As expected, CART colocalized with oxytocin in magnocellular neurons of the supraoptic nucleus. The effects of bromocriptine, a potent dopamine receptor agonist, were examined to determine whether CART mRNA expression and protein release are regulated in a similar fashion as prolactin. Similar to prolactin, CART mRNA expression and protein release were significantly decreased after bromocriptine treatment of dispersed rat anterior pituitary cells in culture. To explore the putative physiological role of pituitary CART, we compared levels of CART mRNA expression in lactating and nonlactating female rats. CART mRNA levels were significantly increased in the anterior pituitary and supraoptic nucleus of lactating rats. Furthermore, levels of CART in the systemic circulation were significantly elevated at the onset of lactation, peaked on d 10 of lactation and returned to baseline values 10 d after pups were weaned. The current study describes the cellular localization and regulation of CART expression and protein release from the rat pituitary gland. These findings suggest a putative role for CART in lactation.
可卡因和苯丙胺调节转录物（CART）是一种高表达的肽，与进食、奖赏和强化以及应激相关行为的调节有关。CART已定位到脑、肠道、肾上腺和胰腺中的离散细胞群体。相比之下，垂体中产生CART的细胞类型仍不清楚。在本研究中，采用我们针对CART-（62-102）产生的高亲和力抗血清进行双标免疫组织化学，以鉴定垂体中产生CART的细胞。在垂体前叶，大多数CART免疫反应性（-ir）定位于催乳素细胞；少数CART-ir细胞被鉴定为生长激素细胞和促肾上腺皮质激素细胞。在垂体后叶，CART-ir与含催产素的纤维广泛共定位；相比之下，只有少数加压素纤维含有CART-ir。正如预期的那样，CART与视上核的大细胞神经元中的催产素共定位。研究了强效多巴胺受体激动剂溴隐亭的作用，以确定CART mRNA表达和蛋白质释放是否与催乳素以类似方式受到调节。与催乳素相似，用溴隐亭处理培养的分散大鼠垂体前叶细胞后，CART mRNA表达和蛋白质释放显著降低。为了探究垂体CART的假定生理作用，我们比较了泌乳和非泌乳雌性大鼠中CART mRNA表达水平。泌乳大鼠垂体前叶和视上核中的CART mRNA水平显著升高。此外，全身循环中的CART水平在泌乳开始时显著升高，在泌乳第10天达到峰值，并在幼崽断奶后10天恢复到基线值。本研究描述了大鼠垂体中CART表达和蛋白质释放的细胞定位及调节。这些发现提示CART在泌乳中具有假定作用。
