Effect Of Mercuric Ions Research Articles

Presynaptic and postsynaptic effects of mercuric ions on guinea-pig ileum longitudinal muscle strip preparation

The toxic effect of mercuric ions on intestinal cholinergic neurotransmission was investigated in vitro. Hg2+ inhibited the evoked release and enhanced the resting release of ACh. Smooth muscle contraction was irreversibly inhibited by Hg2+ in a concentration-dependent manner, and Na2EDTA did not antagonize this effect. We also investigated if Hg2+ enters the nerve terminal through Ca(2+)-channels, or Na(+)-channels, or both. The effects of mercuric ions obtained in our study were completely abolished by the combined administration of TTX and Co2+. It is suggested that the site of the action of mercuric ions is intracellular. We concluded that Hg2+ may interfere with cholinergic transmission by blocking [Ca2+]o-dependent release of ACh and by enhancing [Ca2+]o-independent resting release of ACh. The effect of Hg2+ was not only presynaptic since it also inhibited the effect of ACh on smooth muscle.

Effects of mercuric ions on isolated guinea-pig ileum.

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 microM, 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 microM, observed in depolarized muscle was presumably due to a decreased Ca2+ availability for the contractile process. In the higher concentration range, 1-100 microM, a probably direct action on the contractile elements causing irreversible deterioration of the preparation seems to be present.

The effect of mercuric ions on connective tissue macromolecular synthesis

Hg 2+ at concentrations in the μM range markedly inhibits the synthesis of DNA, RNA collagen and non-collagen proteins, and sulfated proteoglycans, in 10-day-old embryonic chick cartilage explants in vitro. These studies may explain some of the deleterious effects of Hg 2+ on connective tissues.