Molecular aspects of kallikrein and kininogen in the maturing kidney.

Kinins are vasoactive paracrine peptides which participate in a wide range of functions, including the regulation of local organ blood flow, systemic blood pressure, transepithelial water and electrolyte transport, cellular growth, capillary permeability and inflammatory response, and pain. The recent introduction of specific bradykinin receptor subtype antagonists has greatly advanced our understanding of the role of the kallikrein-kinin system (KKS) in various physiological and disease states. However, a major gap remains in our knowledge of the role of kinins in early development. In this review, evidence is presented that the developing nephron expresses both tissue kallikrein and kininogen, and that the genes encoding the components of the KKS are subject to considerable developmental regulation. The activity of the intrarenal kinin-generating system is lowest in the developing kidney and increases with age. Completion of nephrogenesis is characterized by a marked surge in intrarenal kallikrein synthesis and gene transcription. Maturation is associated with redistribution of intrarenal kallikrein and its messenger RNA from the inner to outer cortical nephrons following the centrifugal pattern of nephron development. Challenges for the future include delineation of the direct role of kinins in the maturation of renal functions and elucidation of the molecular mechanisms underlying the developmental expression of the KKS.