[Immunohistochemical study on endothelin in rat kidney].

To elucidate the role of endothelin (ET) in the kidney, we immunohistochemically examined the precise distribution of various forms of ET-peptides in the rat kidney, using specific polyclonal antibodies to each precursor (Big ET-1, Big ET-2 and Big ET-3), and anti-mature ET antibodies. Immunoreactivity of Big ET-1 was localized mainly in some vascular endothelial cells, glomerular mesangial cells and epithelial cells of proximal tubules in the renal cortex and inner-medullary collecting ducts. The distribution of immunoreactivity for mature ETs was similar to those of Big ET-1. These observations suggest that mature ET-1 after conversion from Big ET-1 is secreted from these cells. Since similar findings were obtained using anti-Big ET-2 and anti-Big ET-3 antibodies, these two isopeptides are also considered to have certain physiological actions in the kidney. Immunohistochemical studies for ET-A receptor were also performed. The distribution of this receptor was similar to those of Big ETs and mature ETs. This suggests that secreted ET acts on adjacent cells in an autocrine/paracrine manner in the kidney.