Human urinary trypsin inhibitor (urinastatin)-like substance in mouse kidney and its relationships to mouse kidney kallikrein.

Mouse kidney contains urinastatin (UT)-like immunoreactive substances with trypsin inhibitory activity. Immunohistochemical studies show that these UT-like substances are localized in the same region as kidney kallikrein, i.e. in the distal tubules. Sephadex column chromatography of mouse kidney extract using 0.1M NaCl as the eluent yielded fractions (C.F.) containing both UT-like and kallikrein-like material. In these fractions (C.F.), the removal of UT-like material caused a concomitant decrease in kallikrein-like activity and vice versa. However, when the kidney extract was eluted with an acidic buffer of high ionic strength, the fractions containing both UT-like and kallikrein-like substances were not observed. These results suggest that these two components are intimately bound to one another. The kallikrein activity responded differently to pH, to metal ions (zinc and copper), and to the sodium/potassium ratio, depending on the concomitant presence or absence of UT-like material. These findings suggest that kallikrein activity in kidney tissue is modified by the presence of an UT-like substance.