Expression and cellular localization of kininogens in the human kidney

Human high (H) and low (L) molecular weight kininogens are encoded by distinct mRNAs derived by alternative splicing from a single kininogen gene. Previous studies have demonstrated the presence of L-kininogen but not of H-kininogen in the distal nephron structures of the kidney. Using the highly sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) we have been able to demonstrate the expression of both H-kininogen mRNA and L-kininogen mRNA in kidney and liver. The presence of H- and L-kininogen antigen was shown immunohistochemically by applying specific antibodies that discriminate between the two types of kininogens. Immunoreactive kininogens were localized in the cortical and medullary collecting ducts. Our results indicate that both types of kinin-bearing kallikrein substrates are expressed in the human kidney where they might contribute to the suggested roles of the kallikrein-kinin system in the regulation of renal blood flow and electrolyte excretion.