Development in newborn rats. markedly. During the early postnatal period, in an apelin-deficient mouse, APJ expression and immunostaining in the gut were reduced suggesting that apelin regulates APJ. Together, our data support a role for the apelin-APJ system in regulation of smooth muscle, epithelial and goblet cell function in the GI tract. strong class=”kwd-title” Keywords: expression, immunohistochemistry, localization INTRODUCTION Apelin is the endogenous ligand for the APJ receptor [1]. The APJ receptor is a member of the G-protein-coupled receptor (GPCR) family [2] and is structurally related to the angiotensin and CXC chemokine receptors [3, 4]. Apelin was discovered by screening tissue extracts for their effects on extracellular acidification and inhibition of cAMP formation in a Chinese hamster ovary cell line transfected with the APJ cDNA [1]. Rat, mouse, cow and human apelin cDNAs have been characterized [1, 5] and encode a 77-amino-acid precursor peptide. A 36-amino-acid variant of apelin is the apparent parent peptide. Apelin and APJ have a widespread distribution in the body [6C8]. Apelin and APJ are expressed in the brain, kidney, adipose tissue, heart, lung, retina, mammary gland and gastrointestinal tract (GI) [5, 9C17]. Apelin exerts a broad range of physiological actions including effects on heart contractility, blood pressure, blood vessel growth, appetite and drinking behavior, pituitary hormone secretion and the hypothalamic-pituitary-adrenal axis [17C24]. In the GI tract and pancreas, apelin has been shown to influence gastric acid secretion as well as intestinal and pancreatic hormone secretion [17, 25, 26]. During pregnancy and lactation, breast Oxtriphylline apelin expression increases ~7- to 20-fold [5, 27] and significant amounts of apelin are ingested by neonates. A putative target of ingested Oxtriphylline Oxtriphylline apelin is the GI tract, however, the extent to which APJ is expressed postnatally in the GI tract, and more Rabbit polyclonal to EIF3D importantly, where APJ is localized in the GI tract are not known. The purpose of the present study, therefore, was to characterize APJ and apelin expression (mRNA levels) profiles as well as localization and abundance of APJ protein and apelin peptide in the developing mouse and rat GI tract. Additionally, the influence of apelin gene knockout on APJ mRNA and immunostaining intensity was investigated. MATERIALS AND METHODS Animals All animal experiments were done in accordance with mandated standards of humane care and were approved by the Institutional Animal Care and Use Committees at the University of Texas Medical Branch and Stanford University. C57/BL6 mice (Figure 1 and Figure 3), 129SV mice (Figure 6 and Figure 7) and Sprague-Dawley rats (Figure 1CFigure 5) were maintained in air-conditioned and light-regulated rooms (lights on, 0600C1800 h) and given access to food and water ad libitum. All tissues were harvested from animals in Oxtriphylline the ad lib-fed condition. For generation of embryonic and postnatal tissues, mice and rats were mated in house. Rat and mouse litters were born at approximately 21 and 19.5C20 d gestation and kept with their mothers until 21 d postpartum. As indicated in figure legends, apelin and APJ expression levels were examined at one embryonic (E18.5, mouse; E21, rat) two postnatal (P4, P16) stages, and in the adult (1C3 months of age). For measurement of APJ expression levels or IHC localization of APJ protein in apelin gene knockout and control 129SV mice, GI tissues were harvested at E18.5, P7, P18, and P38. GI tissues were harvested from mice and rats of both sexes and either placed in a reagent called RNA later (Ambion, Austin, TX) or immediately extracted for total cellular RNA. Samples in RNA later were extracted at a.
