Low concentrations of inorganic mercury inhibit in vitro autonomic transmission in the presence of albumin

Abstract

The influence of albumin, 4.5 and 45 g/l, on the effects of Hg²⁺, 10⁻⁹-10⁻³ M, on the neuromuscular transmission of the isolated guinea-pig ileum and vas deferens was investigated. Hg²⁺, 10 ⁹-10 ⁻⁶ M, transiently increased the basal tone of the ileum in Tyrode solution without albumin. Albumin, 4.5 g/l, reversed this stimulant effect but enhanced the contractile response to direct muscle stimulation. This contractile response also increased in the vas deferens. Albumin, 45 g/l, obliterated the stimulant effects of Hg²⁺ on the smooth muscle of the ileum but not of the vas deferens. The effects caused by higher concentrations of Hg²⁺, 10 ⁵-10⁻⁴ M, were only partly inhibited when albumin was present. When neurogenic contractions were elicited in the presence of albumin (45 g/l), Hg²⁺, 10⁻⁹-10⁻⁴ M, reduced the contractions in both organs. Consequently, Hg²⁺ in concentrations presently considered acceptable in blood plasma (10⁻⁹-10⁻⁸ M) suppressed both cholinergic and adrenergic neuromuscular transmission even in the presence of albumin.

Key Words:

• Neuromuscular transmission
• ileum
• mercury
• smooth muscle
• vas deferens