Ureteral contractions induced by rat urine in vitro: probable involvement of renal kallikrein.

Rat urine, even at a 1:10 final dilution in Tyrode's solution, stimulates contraction of the ureteral musculature in vitro. This effect can be ascribed to the presence of kallikrein or a kallikrein-like enzyme in urine. Isometric contractions of ureters were prevented by previous addition of aprotinin to the organ bath. Urine also lost its activity after inactivation of enzymes by heat or acid treatment.