Effects of mercuric ions on isolated guinea-pig ileum

Abstract

The possible physiological significance of low concentrations of Hg²⁺ in the guinea-pig ileum has been investigated. Responses to nerve stimulation by single electrical shocks, acetylcholine (ACh), and histamine (Hi) and the response to ACh of a depolarized preparation were examined. A stimulant effect of Hg²⁺, in the concentration range of 10 nM-1 üM, dominated in intestine accommodated in biological saline solution. This excitatory effect was probably mainly due to stimulation of a depolarization-coupled initiation of the contraction. The inhibitory effect of Hg²⁺, 10 nM-1 üM, observed in depolarized muscle was presumably due to a decreased Ca²⁺ availability for the contractile process. In the higher concentration range, 1-100 üM, a probably direct action on the contractile elements causing irreversible deterioration of the preparation seems to be present. ▪Amalgams; cholinergic transmission; corrosion; excitable tissue; smooth muscle