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Kinetics of glucose transport by the perfused mid‐gut of the freshwater prawn Macrobrachium rosenberg ii.
Author(s) -
Ahearn G A,
Maginniss L A
Publication year - 1977
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1977.sp012002
Subject(s) - phlorizin , phloretin , macrobrachium rosenbergii , fructose , glucose transporter , glucose uptake , chemistry , prawn , kinetics , galactose , biochemistry , sugar , medicine , endocrinology , biophysics , biology , insulin , fishery , physics , quantum mechanics
1. Mucosal influx of [3H]glucose was examined in the mid‐gut of a freshwater prawn, Macrobrachium rosenbergii, using an in vitro perfusion technique. 2. [3H]glucose transfer across the apical cell membrane of the epithelium exhibited Michaelis‐Menten kinetics (Jmax.in = 0‐15 mumole glucose equiv/g. min, Kt = 0‐17 mM). Under Na‐free conditions, glucose influx was significantly reduced and a linear function of substrate concentration, indicative of either slow cellular diffusion (KD = 7‐6 X 10(3) mumole glucose equiv/g. min. mM) or a facilitated process with a low carrier affinity for the sugar. 3. Phlorizin was a potent competitive inhibitor of glucose influx (K1 = 3‐6 X10(‐3) mM), galactose and 3‐O‐methylglucose (3‐O‐MG) were weak inhibitors, and fructose had no evident effect on glucose uptake. Azide, but not iodoacetate (IAA), significantly depressed influx. 4. Absorbed [3H]glucose was rapidly metabolized by the mid‐gut. The majority of accumulated activity within the tissue was in the form of phosphorylated compounds and tritiated water (THO), while only 0‐3% was recovered as a free‐glucose. 5. Preliminary studies examining transmural [3‐H]glucose transport, however, demonstrated a significant net mucosal to serosal free‐glucose flux across the prawn mid‐gut which was Na‐dependent and IAA‐ and phlorizin‐sensitive. Two alternative interpretations of the data are advanced as possible mechanisms for transepithelial glucose transport: (1) group translocation, or (2) the operation of an energized, high affinity, baso‐lateral sugar transport carrier.