Separation of Pancreatic Cardiodepressant Activity into Peptide and Salt Activity 1

Abstract

Summary

The cardiodepressant activity of shock plasma has been ascribed to the presence of a circulating cardiodepressant factor of pancreatic origin. It has been suggested that the activity observed was due to the presence of excess salt in the assay system, rather than a specific pancreatic cardiodepressant peptide (PCP). We wish to report that we obtained cardiodepressant activity (CDA) from an incubated pancreatic homogenate (IPH) (1:6, w/v, in Krebs-Henseleit solution). Heat-precipita-ble proteins of the IPH were removed by heating (80°) and centrifugation, the clear supernatant was subjected to ultrafiltrations, and the fraction below a molecular weight of 1000 was applied to a Sephadex G-10 column. This material was separated into 40 fractions, and each fraction was lyophilized and reconstituted with 15 ml of Krebs-Henseleit buffer. The fractions were then assayed for Na⁺, K⁺, Cl^-, and Ca²⁺ concentrations as well as CDA activity in the isolated cat papillary muscle (PM) assay system. The IPH was resolved into several uv-absorbing peaks (A ₂₈₀). The CDA was associated with the nonretarded peptide peak and the salt peak. No salts, as detected by flame photometries, were present in the nonretarded peptide peak. Raising the Na⁺ concentration in the KH buffer and testing it in the PM system revealed that CDA increased proportionally to NaCl content. Thus, it appears that CDA of IPH can be separated into a peptidic depressant fraction which is distinct from the salt depressant fraction.

We would like to thank Dr. Harold Brown and Ms. Elizabeth Korniat for their help in the ion determinations. We would also like to thank Ms. Susan Benvin, Ms. June Eisenmann, and Mr. Ted Ganzler for the excellent technical assistance.