Renal tissue kallikrein in newborn and young SHR

Since young SHR excrete less urinary kallikrein than WKY, active and total kallikrein (A and T Kall, respectively) was measured (amidolytic assay) in the renal cortex of both strains. Neither at birth nor at age 4 weeks did renal T Kall differ between SHR and WKY. Renal A Kall was significantly lower in newborn SHR and higher in 4-week-old-SHR than in age-matched WKY. Our results indicate that urinary kallikrein does not accurately reflect the renal enzyme activity. They suggest that SHR exhibit an inherited defect in prokallikrein activation and a secondary defect in the release of tissue kallikrein into urine.