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Tonin and kallikrein-kinin system
M H Feitosa1, J L Pesquero, M A Ferreira
1Department of Physiology and Biophysics, Federal University of Minas Gerais, Brazil.
Advances in Experimental Medicine and Biology
|January 1, 1989
Summary
Rat uterine contractions induced by tonin suggest two distinct kininogenase substrates. Desensitization experiments reveal specific interactions between tonin, kallikrein, and uterine muscle.
Area of Science:
- Biochemistry
- Pharmacology
- Physiology
Background:
- Tonin, an enzyme from the rat submandibular gland, possesses kininogenase activity.
- Previous studies have demonstrated the kininogenase activity of tonin.
Purpose of the Study:
- To investigate the mechanism of rat uterine contraction induced by tonin.
- To explore the potential presence of distinct substrates for tonin and kallikrein in the rat uterus.
- To elucidate the relationship between tonin, kallikrein, and kinin release.
Main Methods:
- Uterine contraction assays using isolated rat uteri.
- Enzyme desensitization experiments with tonin, kallikrein, and trypsin.
- Parallel uterus preparations to assess kinin release.
Main Results:
- Tonin induced rat uterine contractions, which were subject to desensitization upon repeated exposure.
- Desensitization to tonin significantly reduced subsequent contractions induced by kallikrein, but not vice versa.
- Desensitization to trypsin abolished tonin-induced contractions.
- Experiments suggested the release of kinin during tonin-mediated uterine contraction.
Conclusions:
- The rat uterus likely contains at least two distinct kininogenase substrates, with differential specificity for tonin and kallikrein.
- Tonin's action on the uterus involves kinin release, mediated by a trypsin-sensitive substrate.
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