Expression of urocortin III/stresscopin in human heart and kidney

Urocortin III (Ucn III)/stresscopin (SCP) is a novel peptide of the corticotropin-releasing factor (CRF) family and is a specific ligand for the CRF type 2 receptor. We wished to clarify whether Ucn III/SCP is expressed in the human heart and kidney. Immunoreactive Ucn III was detected by RIA in the human heart (0.74-1.15 pmol/g wet weight, mean ± SEM; n = 4) and kidney (1.21 ± 0.30 pmol/g wet weight), which were obtained at autopsy. These levels were comparable to the levels in pituitary (2.72 ± 0.13 pmol/g wet weight; n = 3) and brain tissues (∼1-2 pmol/g wet weight). Furthermore, immunoreactive Ucn III was present in human plasma (51.8 ± 16.0 pmol/ liter, n = 5) and urine (266 ± 20 pmol/liter; n = 5) obtained from healthy subjects. Reverse-phase HPLC showed a broad peak of immunoreactive Ucn III eluting in the position of synthetic Ucn III in the heart, kidney, and hypothalamus. Material eluting in the position of SCP was also found in the HPLC analysis of these tissue extracts. Immunocytochemistry showed positive staining of Ucn III in the myocardium and the renal tubules, particularly distal tubules. RT-PCR showed expression of Ucn III mRNA in the brain, pituitary, heart, and kidney. The present study has shown expression of Ucn III/SCP in the human heart and kidney as well as brain and pituitary tissues and its presence in plasma and urine. Ucn III/SCP may therefore regulate the cardiac and renal function as a local factor and a circulating hormone.