Lymphatic, renal, and urinary kallikreins in the rat

In pentobarbital-anesthetized rats the lymphatic vessels next to the renal artery and the urinary bladder were cannulated and lymph and urine were collected for 3 h. The kidneys were then washed and removed. Four experimental groups were studied. Kallikrein was measured in lymph, urine, and kidney extracts by a direct radioimmunoassay. Immunoreactive renal and urinary kallikreins were higher in a Na-deficient group. No changes were brought about by furosemide administration or Na supplementation. A very low concentration of immunoreactive kallikrein was found in lymph, with no differences between the groups. In the same urine and kidney extract samples, both total (trypsin-activated) kallikrein and naturally active kallikrein were determined as kininogenase activity in the rat uterus bioassay. Both active and inactive kallikreins were found in kidney and urine, but most of the changes induced by a Na-deficient diet or furosemide administration were restricted to the active form. It is suggested that the lymphatic route in the kidney is probably not an important source of circulating immunoreactive glandular kallikrein.