Meeting Abstract

P1.53  Wednesday, Jan. 4  Comparative sugar transport by crustacean hepatopancreas and intestine DUKA, A.*; AHEARN, G.A.; U. of North Florida, Jacksonville; U. of North Florida, Jacksonville

Crustacean hepatopancreas and intestine are both sites of nutrient absorption. Glucose is transported in both organs by Na-dependent cotransport, while Na-dependent D-fructose influx has also been described for the hepatopancreas. In neither organ have the details of ion dependent sugar transport been elucidated and it is still unclear as to whether 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 Na-dependency of both 3H-D-glucose and 3H-D-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 mM (glucose) and 2.58 +/- 0.95 mM (fructose). Both sugars displayed significant (p < 0.01) Na-dependent and Na-independent uptake processes. Transepithelial 0.025 mM 3H-D-glucose and 3H-D-fructose fluxes across lobster intestine over a luminal sodium concentration range of 1 – 50 mM were hyperbolic functions of luminal [Na+], displaying Km values of 6.05 +/- 0.99 mM (glucose) and 10.58 +/- 1.65 mM (fructose). As with hepatopancreatic sugar transport, transepithelial intestinal sugar transport exhibited both significant (p < 0.01) Na-dependent and Na-independent processes. Similar sodium dependency of glucose and fructose transport in both gut organs suggests that they may be transported by carrier processes with physiological properties considerably different than those of mammalian transporters.