Effects of ouabain and 2,4-dinitrophenol on Ca exchange in taenia coli

Abstract

High K produces in the guinea pig taenia coli a tonic contracture which is abolished by 2,4-dinitrophenol [DNP] (10-4 M) and ouabain (2. 5 x 10-6 M). Experiments were conducted to further delineate the movement of Ca during the abolition of the tonic contracture by ouabain and DNP. Tissue Ca and Ca45 uptake determinations revealed that both these factors were deceased to control levels during the abolition of tension by ouabain, but that the tissue Ca level remained elevated in the presence of DNP. The findings led to the belief that these 2 agents were affecting the K-induced contracture by different mechanisms. To judge on the assumption that the K-induced tonic contracture depends on a metabolically dependent transport and exchange of Ca, it appears that DNP blocks metabolism, with the result that the Ca-extrusion mechanism becomes depressed, as well as proposed metabolically dependent process that keeps the Ca entering the fiber in an exchangeable form. The effects of ouabain are interpreted as possibly affecting the K-induced Ca transport process at the fiber membrane, and since ouabain is known to inhibit many Na-dependent transport processes, it is possible that this Ca transport process is coupled to an active Na efflux.