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Effects of intestinal insulin‐like peptide on glucose catabolism in mealworm larval fat body in vitro: Dependence on extracellular Ca 2+ for its stimulatory action
Author(s) -
Mtioui Abdelhamid,
Gourdoux Lucienne,
Fournier Bernard,
Moreau Robert
Publication year - 1993
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.940240302
Subject(s) - mealworm , insulin , biology , medicine , ionomycin , endocrinology , biochemistry , glucose uptake , catabolism , metabolism , in vitro , egta , extracellular , calcium , larva , botany
In vitro hormonally induced variations of glucose catabolism in mealworm fat body tissue were examined by a microradiorespirometric method. An insulin‐like peptide (ILP) extracted from the midgut of last larval instar mealworm larvae significantly modified glucose catabolism and was dependent on energy metabolism and on the Ca 2+ concentration in the culture medium. Using two different labelled substrate molecules, the stimulatory effects of ILP (compared with those of mammalian insulin) on the relative use of the pentose cycle as opposed to the glycolytic‐citric acid cycle by the mealworm fat body were measured in vitro. Metabolic variations were evaluated using either [1‐ 14 C]glucose or [6‐ 14 C]glucose as substrates. Time course and dose‐response curves of ILP and the hormonally induced variations in total CO 2 and 14 CO 2 kinetics were determined. Modification in the specific radioactivity kinetics of 14 CO 2 derived from [1‐ 14 C] glucose and [6‐ 14 C] glucose molecules under hormonal effects were observed. As demonstrated in in vivo studies, ILP stimulated the relative utilization of the pentose cycle. However, this effect was observed much more rapidly, but for a shorter time, with fat body in vitro. Mammalian insulin produced similar, but not identical effects. Variations in transmembranous Ca 2+ cellular exchanges, induced by either EGTA, nifedipine, or calcium ionophore ionomycin included in the culture medium, indicated that the stimulatory effects of ILP depends on this cation. © 1993 Wiley‐Liss, Inc.