Year

2013

Season

Summer

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)

Department

Biology

NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Gregory Ahearn

Second Advisor

Dr. Judith Ochrietor

Third Advisor

Dr. James Gelsleichter

Department Chair

Dr. Daniel C. Moon

College Dean

Dr. Barbara A. Hetrick

Abstract

Glucose is transported in crustacean hepatopancreas and intestine by Na+-dependent co-transport, while Na+-dependent D-fructose influx has only been described for the hepatopancreas. It is still unclear if the two sugars are independently transported by two distinct cotransporter carrier systems. In this study lobster (Homarus americanus) hepatopancreas brush border membrane vesicles (BBMV) were used to characterize, in detail, the cation-dependency of both D-[3H] glucose and D-[3H] fructose influxes, while in vitro perfused intestines were employed to determine the nature of cation-dependent sugar transport in this organ. Over the sodium concentration range of 0-100 mM, both 3H-D-glucose and 3H-D-fructose influxes (0.1 mM; 1 min uptakes) by hepatopancreatic BBMV were hyperbolic functions of [Na+], exhibiting Km values of 2.30 ± 0.59 and 2.58 ± 0.95 mM, respectively. D-[3H] glucose and fructose influxes by hepatopancreatic BBMV over a potassium concentration range of 15-100 mM were hyperbolic functions of [K+], exhibiting Km values of 9.85 ± 0.41 and 12.6 ± 0.80 mM respectively. Both sugars displayed significant (p < 0.01) Na+/K+-dependent and Na+-independent uptake processes. Transepithelial 25 μM D-[3H] glucose and D-[3H] fructose fluxes across lobster intestine over a luminal sodium and potassium concentration range of 0 – 50 mM and 5-100 mM, respectively, were hyperbolic functions of luminal [Na+] and [K+]. As with hepatopancreatic sugar transport, transepithelial intestinal sugar transport exhibited both significant (p < 0.01) Na+/K+-dependent and Na+-independent processes. Results suggest that both D-glucose and D-fructose are transported by a single carrier process in each organ with sodium being the preferred cation for both sugars in the hepatopancreas, and potassium being the preferred cation for both sugars in the intestine.

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