Meeting Abstract
P1.52 Wednesday, Jan. 4 K-dependent 3H-D-glucose transport by hepatopancreatic BBMV of the marine shrimp, Litopenaeus setiferus. OBI, I.*; STERLING, K.M.; SIMMONS, T.; AHEARN, G.A.; U of North Florida, Jacksonville; U of North Florida, Jacksonville; U of North Florida, Jacksonville; U of North Florida, Jacksonville gahearn@unf.edu
This study reports the occurrence and properties of K-dependent 3H-D-glucose transport across hepatopancreatic brush border membrane vesicles (BBMV) of the marine shrimp, L. setiferus, and speculates on the possible biological relevance of this phenomenon. Vesicles loaded with 300 mM mannitol and incubated in 0.1 mM 3H-D-glucose and either 150 mM NaCl or 150 mM KCl both exhibited 3H-D-glucose uptake overshoots at 1 min of incubation that were approximately twice equilibrium, suggesting that both cations could equally drive sugar accumulation. 3H-D-glucose influxes (1 min uptakes; 0.1 mM D-glucose) in the presence of inwardly-directed 150 mM KCl or 150 mM NaCl gradients were significantly (p < 0.05) stimulated by an inside-negative membrane potential (pHi = 5.0; pHo = 7.0; 50 micro-M CCCP), and significantly (p = 0.05) inhibited by 0.25 mM phloridzin. Certain sugars at 0.1 mM significantly (p = 0.05) reduced influx of 0.1 mM 3H-D-glucose in 150 mM KCl (e.g., D-mannose and 2-deoxy-D-glucose), while others (e.g., D-galactose, alpha-methyl-D-glucoside, D-fructose) were without effect. In the presence of an imposed inside negative membrane potential, 3H-D-glucose (0.1 mM) influx was a hyperbolic function of variable external [KCl] (25 to 400 mM), and had a lower Km and higher Jmax than a similar curve displayed by vesicles without a membrane potential. Membrane potential had the greatest effect on the apparent binding affinity (e.g., Km) of the D-glucose transport system. Results suggest the presence of a brush border K-D-glucose cotransport system in these largely herbivorous shrimp which uses dietary K to stimulate sugar uptake. Project supported by USDA agriculture and food research initiative competitive grant no. 2010-65206-20617.
