Experiments on the factor in urine forming substance U

A hypotensive and smooth muscle contracting substance, provisionally termed substance U, is formed on incubation of dog's urine with dog's serum (Beraldo, 1952, 1955). The factor in urine which forms this substance is non-dialysable, thermolabile and precipitated by 80% ethanol. Substance U itself is formed from the pseudoglobulin fraction of the plasma. There is a striking similarity between the factor in urine forming substance U and kallikrein, which according to Frey, Kraut & Schultz (1930) is a circulatory hormone of pancreatic origin which is eliminated in the urine. The question therefore arose whether the factor forming substance U is also of pancreatic origin. According to Frey et al. (1930) removal of the pancreas is followed within a few hours by a reduction of 85% in the kallikrein in urine; and this reduction persists for weeks after the operation. According to Werle (1955), however, the reduction does not occur during the first few hours after the operation and requires 1 or 2 weeks to develop. A reduction in the kallikrein content of urine was also found by Frey et al. (1930) to occur following occlusion of the pancreatic blood vessels. On the other hand, when the circulation was re-established 1-2 hr later, the kallikrein content of urine increased to about 3 times its original level. Frey et al. (1930) state further that injection of insulin into pancreatectomized dogs caused a gradual increase in the kallikrein content of urine, the pre-operation level being reached within 2 hr. The present experiments deal with the effect of exclusion of the pancreas either by occlusion of the pancreatic blood vessels, or by removal of the pancreas in acute and chronic experiments, on the output of the factor in urine forming substance U. The urinary output of this factor was also studied in the