Effects of zinc on l-

Area of Science:

• Marine Biology
• Environmental Toxicology
• Biochemistry

Background:

• The hepatopancreas is crucial for nutrient absorption in crustaceans.
• Understanding heavy metal effects on nutrient transport is vital for ecological health.
• Brush-border membrane vesicles (BBMVs) are models for studying nutrient uptake.

Purpose of the Study:

• To investigate the impact of divalent heavy metals on l-[(3)H]proline uptake in lobster BBMVs.
• To determine the specific effects of zinc on proline transport kinetics.
• To elucidate the mechanism of zinc-mediated enhancement of amino acid transport.

Main Methods:

• Preparation of lobster hepatopancreas BBMVs using magnesium precipitation.
• Transport assays measuring l-[(3)H]proline uptake under various metal ion conditions.
• Kinetic analysis of proline influx in response to zinc concentration.
• Inhibition studies using l-pipecolate to identify the transport system.

Main Results:

• High external concentrations of Cd(2+), Cu(2+), Fe(2+), Mn(2+), and Zn(2+) inhibited l-[(3)H]proline uptake.
• Pre-incubation with these metals, particularly zinc, significantly enhanced proline transport.
• Zinc increased the maximal rate (J(max)) of proline influx but not binding affinity (K(m)).
• Zinc-stimulated uptake was mediated by the Na(+)-dependent, l-pipecolate-sensitive IMINO transport system.

Conclusions:

• Divalent heavy metals have complex effects on amino acid transport in lobster BBMVs.
• Zinc can enhance proline uptake by modulating the IMINO transporter's maximal capacity.
• The findings suggest a potential mechanism for heavy metal interaction with nutrient transport systems in marine invertebrates.