The precursors of kinins, K-kininogens and T-kininogens (KG), are encoded by separate genes that display 90% nucleotide sequence homology. Despite their homology, K-KG and T-KG genes are differentially regulated. The K-KG gene is expressed constitutively and encodes high- and low-molecular-weight KG, the precursors of the vasoactive nonapeptide bradykinin. In contrast, the T-KG gene is inducible, and its protein is a potent thiol-protease inhibitor. Given their potential role in the regulation of blood pressure, renal hemodynamics, and the response to inflammation and tissue injury, K-KG and T-KG gene expression in rats subjected to chronic (1 or 5 wk) unilateral ureteral obstruction (UUO), a maneuver that suppresses renal kallikrein synthesis to 25% of controls, has been examined. Northern and slot blots of total liver and kidney RNA were probed with oligonucleotides complementary to either T-KG or K-KG mRNA under high-stringency conditions. Steady-state levels of hepatic T-KG mRNA were increased in the UUO compared with sham-operated rats--2.7-fold at 1 wk and 4.1-fold at 5 wk (P < 0.05). Western blot analysis revealed that the 68-kd T-KG protein was up-regulated 2.5- to 3-fold in the liver of UUO rats (P < 0.05). In marked contrast, the abundance of high (2.3-kb)- and low (1.6-kb)-molecular-weight splicing transcripts of hepatic pre-K-KG mRNA was not altered at either time after UUO.(ABSTRACT TRUNCATED AT 250 WORDS)