Evidence for the presence of a glucosensor in hypothalamus, hindbrain, and Brockmann bodies of rainbow trout.
The aim of this study was to evaluate the existence of a glucosensor in different regions of the brain and in the Brockmann bodies (BB) of the rainbow trout, Oncorhynchus mykiss. Five groups (n = 12) of trout were injected intraperitoneally with saline alone (control) or saline-containing bovine glucagon (100 mug/kg), bovine insulin (4 mg/kg), 2-deoxy-d-glucose (100 mg/kg), or d-glucose (500 mg/kg) to promote hyperglycemia (glucagon, d-glucose, 2-deoxy-d-glucose) or hypoglycemia (insulin). Six hours after injection, samples from four brain regions (hypothalamus, telencephalon, hindbrain, and midbrain) and the entire BB were taken. Our results demonstrate within the BB and both the hypothalamus and hindbrain a metabolic response different to that observed in other tissues (midbrain, telencephalon) but similar to that described in tissues known to be glucosensors in mammals. The metabolic responses of these areas to changes in plasma glycemia were characterized by parallel changes in GLUT-2 expression, hexokinase-IV, or glucokinase activity and expression, glycolytic potential, and levels of glycogen and glucose. These changes are similar to those reported in mammalian pancreatic beta-cells and glucose-excited (GE) neurons, two cell types containing glucosensors. This study provides evidence for the presence of glucosensors responsive to hyper- and hypoglycemia in rainbow trout BB, hypothalamus, and hindbrain.
Polakof
Sergio
S
Laboratorio de Fisioloxía Animal, Facultade de Bioloxía, Edificio de Ciencias Experimentais, Universidade de Vigo, E-36310 Vigo, Spain.
Míguez
Jesús M
JM
Moon
Thomas W
TW
Soengas
José L
JL
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002417:Cattle; D003847:Deoxyglucose / Q000008:administration & dosage / Q000494:pharmacology; D005934:Glucagon / Q000008:administration & dosage / Q000494:pharmacology; D005941:Glucokinase / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D051273:Glucose Transporter Type 2 / Q000235:genetics / Q000378:metabolism; D006003:Glycogen / Q000032:analysis; D006593:Hexokinase / Q000235:genetics / Q000378:metabolism; D006728:Hormones / Q000008:administration & dosage / Q000494:pharmacology; D006943:Hyperglycemia / Q000139:chemically induced; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology; D007031:Hypothalamus / Q000378:metabolism*; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008636:Mesencephalon / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012249:Rhombencephalon / Q000378:metabolism*; D013687:Telencephalon / Q000378:metabolism; D013997:Time Factors
D001786:Blood Glucose; D051273:Glucose Transporter Type 2; D006728:Hormones; D007004:Hypoglycemic Agents; D007328:Insulin; D006003:Glycogen; D005934:Glucagon; D003847:Deoxyglucose; D006593:Hexokinase; D005941:Glucokinase; D005947:Glucose