Systemic distribution of salusin expression in the rat

Salusin-alpha and salusin-beta are multifunctional bioactive peptides with hypotensive and bradycardic effects. They were originally identified from full-length human cDNAs by bioinformatics analyses. Salusin peptides are expressed in human tissues at the mRNA level, but no information is available about their systemic distributions in any species. We examined the distributions of preprosalusin mRNA and the salusin peptides in a variety of normal rat organs. Whereas preprosalusin mRNA was expressed ubiquitously, immunoreactive salusin-beta was detected most strongly in the hypothalamus and posterior pituitary, and less abundantly in the anterior pituitary and gastrointestinal, immune, and hematopoietic systems. Salusin-beta-positive cells appeared to be of either hematopoietic or endocrine origin, and many hematopoietic cells were also stained with anti-CD68, which specifically recognizes macrophages. Salusin-alpha-like immunoreactivity was not detected in any of the rat tissues. These results indicate that rat salusin is immunologically similar to human salusin-beta and widely expressed, especially in the immune, gastrointestinal, and central nervous systems and mainly in endocrine- and hematopoietic-derived cells.