ISSN:
1432-0703
Source:
Springer Online Journal Archives 1860-2000
Topics:
Energy, Environment Protection, Nuclear Power Engineering
,
Medicine
Notes:
Abstract The effect of mercuric chloride (HgCl2) and monomethyl mercury chloride (CH3HgCl) on unidirectional22Na and45Ca influx were measured in the freshwater isopodAsellus aquaticus. Flux measurements involved short-term (20 min) exposure to22Na or45Ca following 2 h pre-exposure to Hg. Experiments were conducted at two different Na and Ca concentrations, 0.025 mmol L−1 and 0.25 mmol L−1. HgCl2 and CH3HgCl inhibited Na influx at both Na concentrations although Na influx at 0.25 mmol L− was always higher. This reflected the uptake kinetics of the Na pump which was determined to be saturable with a kmax values of 32 μmol Na g−1 h−1 and a Km value of 0.8 mmol L−1. CH3HgCl generally resulted in relatively greater inhibition of Na influx. At 0.025 mmol NaL−1 all CH3HgCl concentrations tested were inhibitory to Na influx, i.e., the lowest observed effect concentration (LOEC) was 〈0.04 μmol L−1. Ca influx was inhibited by HgCl2 at all concentrations tested (LOEC 〈0.04). The degree of inhibition was unaffected by Ca concentration, which was seen as evidence for non-competitive inhibition. However, CH3HgCl, which inhibited Ca influx from 0.025 mmol Ca L−1 by 〉68% at molar Hg concentrations ≥1 μmol L−1 showed no significant inhibitory affect at 0.25 mmol Ca L−1. Elimination of CH3HgCl inhibition at the higher Ca concentration suggests competition in this case, possibly at the level of access to the Ca pump.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01183879
