Cation-dependent nutrient transport in shrimp digestive tract.

Area of Science:

• * Marine Biology
• * Crustacean Physiology
• * Molecular Transport Mechanisms

Background:

• * Brush border membrane vesicles (BBMV) from Atlantic White shrimp (Litopeneaus setiferus) hepatopancreas were utilized.
• * Standard methods adapted from mammalian tissues were employed for vesicle purification.
• * Previous studies applied similar methods to other invertebrate epithelia.

Purpose of the Study:

• * To investigate the cation dependency of sugar and amino acid transport across shrimp hepatopancreas luminal membranes.
• * To identify potential coupled transport systems utilizing sodium or potassium gradients.
• * To explore the role of metallic cations in nutrient absorption.

Main Methods:

• * Preparation of purified epithelial brush border membrane vesicles (BBMV).
• * Measurement of radiolabeled (3H) D-glucose, L-histidine, and L-leucine uptake under varying cation gradients.
• * Kinetic analysis of amino acid uptake in the presence of metallic cations (Zn2+, Mn2+).

Main Results:

• * Glucose uptake was driven by either sodium or potassium gradients, indicating a flexible transport system.
• * L-histidine transport was potassium-dependent, while L-leucine showed both sodium and potassium dependency.
• * Metallic cations (Zn2+, Cu2+, Mn2+, Cd2+, Co2+) significantly stimulated L-leucine uptake, with Mn2+ and Zn2+ exhibiting Michaelis-Menten kinetics for L-histidine transport.

Conclusions:

• * The Atlantic White shrimp hepatopancreas possesses multiple cation-dependent nutrient transporters on its brush border membrane.
• * These systems are crucial for the absorption of essential dietary sugars and amino acids.
• * The findings highlight the complex interplay between cations and nutrient transport in crustaceans.