The Effect of Heavy Metals on the Uptake of L-Histidine by the Polychaete Nereis Succinea

Abstract

Integumentary uptake of 3H-L-Histidine by Nereis succinea was measured in the presence and absence of selected heavy metals and inhibitors in 60% artificial seawater (ASW). At low concentrations of L-Histidine (10 uM), metals stimulated L-Histidine uptake from ASW. Higher concentrations of metal inhibited L-Histidine uptake. In amino acid kinetic experiments, 0.5 uM Zn2+ significantly (P < 0.003) increased both L-Histidine influx Jmax (control: 4.7 ± 0.4; treatment: 15.3 ± 1.7 nmol/g dry weight x 15 min), and Km (control: 23.8 ± 5.1; treatment: 44.0 ± 8.8 uM). Fe3+ (0.5 uM) stimulated influx of 10 uM L-Histidine (Jmax = 6.9 ± 0.4 nmol/g dry wt x 15 min; Km = 86.7 ± 12.3 uM), but neither Ag+ nor Al3+ significantly (P > 0.05) altered amino acid influx. L-Leucine (25 uM) reduced Zn2+ -stimulated L-Histidine influx, suggesting a possible role of the Na-independent L-transport system in metal-stimulated L-Histidine transport by worm integument.