D-glucose transport in decapod crustacean hepatopancreas

Physiological mechanisms of gastrointestinal absorption of organic solutes among crustaceans remain severely underinvestigated, in spite of the consid erable relevance of characterizing the routes of nutrient absorption for bo th nutritional purposes and formulation of balanced diets in aquaculture. S everal lines of evidence attribute a primary absorptive role to the digesti ve gland (hepatopancreas) and a secondary role to the midgut (intestine). A mong absorbed organic solutes, the importance Of D-glucose in crustacean me tabolism is paramount. Its plasma levels are finely tuned by hormones (crus tacean hyperglycemic hormone, insulin-like peptides and insulin-like growth factors) and the function of certain organs (i.e. brain and muscle) largel y depends on a balanced D-glucose Supply. In the last few decades, D-glucos e absorptive processes of the gastrointestinal tract of crustaceans have be en described and transport mechanisms investigated, but not fully disclosed . We briefly review our present knowledge Of D-glucose transport processes in the crustacean hepatopancreas. A discussion of previous results from exp eriments with hepatopancreatic epithelial brush-border membrane vesicles is presented. In addition, recent advances in our understandings of hepatopan creatic D-glucose transport are shown, as obtained (1) after isolation of p urified R-, F-, B- and E-cell suspensions from the whole organ by centrifug al elutriation, and (2) by protein expression in hepatopancreatic mRNA-inje cted Xenopus laevis oocytes. In a perspective, the applicability of these n ovel methods to the study of hepatopancreatic absorptive function will cert ainly improve our knowledge of this structurally complex organ. (C) 2001 El sevier Science Inc. Ail rights reserved.