Tonin and kallikrein-kinin system.

The kininogenase activity of tonin has been demonstrated by Ikeda and Arakawa, 1984. Tonin of the rat submandibular gland contracts the rat uterus independent of addition of the substrate. On repetition, the same dose of enzyme elicited desensitization. When a double dose was used the contraction again occurred. After desensitization to tonin the contraction to kallikrein was reduced about 80% of the control. The desensitization to kallikrein lightly reduced the contraction to tonin. When the muscle was desensitized to trypsin tonin did not evoke contraction. These experiments suggest the presence of two different substrates in the uterus, one more specific to kallikrein and the other for tonin. The experiments with the parallel uterus preparation strongly suggest release of kinin in the process of contraction of the uterus by tonin.