Human urinary kinin excretion.

It has been shown that the isolated rat duodenum relaxes in the presence of low concentrations of plasma and urinary kinin. The tissue is at least as sensitive as the rat uterus. Vasopressin and oxytocin, in large doses, also caused relaxation of the duodenum whereas acetylcholine, substance P and 5-hydroxytryptamine caused contraction. It was concluded that if an extract is assayed on the rat uterus and the rat duodenum in parallel using plasma kinin as a standard, and the results agree, this is good evidence that the active principle being estimated is a kinin. This method is therefore both sensitive and specific for kinin estimations, but it will not distinguish between kinins of different origin. The urinary excretion of kinin in 14 healthy adults was found to be fairly constant. The minute output was unaffected by the rate of urine formation, urinary pH, or time of day. There was no increase during sweating or salivation.