Distribution of urocortin 2 in various tissues of the rat

Urocortin (Ucn) 2 is a new member of the corticotrophin-releasing hormone (CRH) neuropeptide family that is expressed in the central nervous system and peripheral tissues. However, the expression levels of Ucn 2 in various tissues of the rat remains unclear. Thus, the aim of the present study was to characterise the expression of Ucn 2 in the various tissues of the rat. Reverse transcriptase-polymerase chain reaction analysis demonstrated that Ucn 2 mRNA is expressed in the hypothalamus, pituitary, adrenal, stomach, skin, ovary, uterus and skeletal muscle. Histologically, Ucn 2 mRNA and Ucn 2-like immunoreactivity (LI) were demonstrated in both the anterior and intermediate lobes of the pituitary, but not detected in the posterior lobe. Furthermore, all Ucn 2-positive cells in the anterior and intermediate lobes were also positive for beta-endorphin. Ucn 2 mRNA was detected in the adrenal cortex and medulla although Ucn 2-LI was only found in the adrenal medulla. High-performance liquid chromatography analysis of hypothalamic, pituitary, and adrenal extracts showed that the main Ucn 2-LI peak occurred at the same molecular size as that of synthetic Ucn 2. These results suggest that Ucn 2 is synthesised in various tissues, including the anterior and intermediate lobes of the pituitary and the adrenal.