INTRAMUSCULAR DELIVERY OF RAT KALLIKREIN-BINDING PROTEIN GENE REVERSES HYPOTENSION IN TRANSGENIC MICE EXPRESSING HUMAN TISSUE KALLIKREIN

The tissue kallikrein-kinin system has been postulated to play a role in blood pressure regulation. The activity of tissue kallikrein is con trolled by a number of factors in vivo. Rat kallikrein-binding protein (RKBP) is a serine proteinase inhibitor which binds to and inhibits t issue kallikrein's activity in vitro. We have recently developed sever al hypotensive transgenic mouse Lines which express human tissue kalli krein. In order to investigate the role of RKBP in blood pressure regu lation, we delivered the RKBP to these transgenic mice by intramuscula r injection. Expression of the RKBP was detected in skeletal muscle by reverse transcription-polymerase chain reaction and Southern blot ana lysis at 10, 20, 30, and 40 days post-injection. Immunoreactive RKBP l evels in the muscle and serum of these mice were quantified by a RKBP- specific enzyme-linked immunosorbent assay and Western blot analysis. The levels of RKBP mRNA and immunoreactive protein were detectable at 10 days post-injection and increased significantly at 20 and 30 days, During this period, RKBP delivery significantly increased systemic blo od pressure in the kallikrein transgenic mice to a level comparable to that of normotensive control mice. The RKBP and vector DNA delivery h ad no effect on the blood pressure of normotensive control mice. No se rum antibodies to RKBP or its DNA were detected in the mice 40 days po st injection. These results suggest that the increase of systemic bloo d pressure by RKBP delivery in these hypotensive transgenic mice may b e mediated by inhibiting tissue kallikrein activity.