Clinical Reviews in Allergy and Immunology 9 Copyright 1998 by Humana Press Inc. 1080-0549/98/385-401/$12.25 Kinin Receptors Francois Marceau* and Dimcho R. Bachvarov Centre Hospitalier Universitaire de Quebec, Centre de Recherche du Pavilion I'H6teI-Dieu de Qu6bec, Qu6bec, Canada G1R 2J6; E-mail: Francois.Marceau@crhdq.ulaval.ca Introduction The major, but not exclusive interface between the kallikrein-kinin system and cellular functions is the action of bradykinin (BK) and related peptides (the kinins) on highly specific receptors expressed by definite cell types. Indeed kinins, positively charged peptides (see Table 1 for structure), influence tissues and cells essentially by stimulating membrane receptors. Pharmacologic investigations dating back to the late 1970s have resulted in a receptor classification (B1 and B2) that is now supported by extensive molecular biology findings, and has influ- enced advances in medicinal chemistry and clinical pharmacology. Among more recent developments, the discovery of allelic polymor- phisms in the human kinin receptor genes allows a fresh approach in the understanding of the kinin role in inflammatory and renal disease. Kinin Receptor Classification Initial structure-activity studies of BK-related peptides indicated that all BK fragments were nearly inactive in the most popular pharma- cologic assay systems (e.g., contractility of the guinea pig ileum, rat uterus, and hypotension in the rat (1). Lys-BK (kallidin) was approxi- mately equipotent to BK in these systems, and des-Argg-BK, inactive, thus indicating that arginine carboxypeptidases commonly termed kininase I represented one of the inactivation pathways of kinins (2). The first hint of the duality of kinin receptor molecule originated from the very atypical structure-activity relationship observed for the con- tractile effect of BK and its fragments in the isolated rabbit aorta (3). It *Author to whom all correspondence and reprint requests should be addressed. Clinical Reviews in Allergy and Immunology 385 Volume 16, 1998