1. In vivo effects of glucose and insulin on secretion and gene expression of glucagon in rats
- Author
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Nadim Kassis, Luc Pénicaud, Christophe Magnan, Alain Ktorza, M C Laury, Marc Gilbert, J. Philippe, Laboratoire de physiopathologie de la nutrition (LPN), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Métabolisme Plasticité et Mitochondrie [lié à l'ex IFR 31] (LMPM), IFR 31 Louis Bugnard (IFR 31), Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Toulouse [Toulouse]-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Toulouse [Toulouse]-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Blood Glucose ,endocrine system ,medicine.medical_specialty ,medicine.medical_treatment ,Glucagon Measurement ,030209 endocrinology & metabolism ,Hypoglycemia ,Arginine ,Glucagon ,03 medical and health sciences ,0302 clinical medicine ,Endocrinology ,Internal medicine ,medicine ,Hyperinsulinemia ,Animals ,Insulin ,RNA, Messenger ,Rats, Wistar ,ComputingMilieux_MISCELLANEOUS ,gamma-Aminobutyric Acid ,030304 developmental biology ,0303 health sciences ,Chemistry ,Glucagon secretion ,nutritional and metabolic diseases ,medicine.disease ,Rats ,Glucose ,medicine.anatomical_structure ,Gene Expression Regulation ,Female ,Pancreas ,[SDV.AEN]Life Sciences [q-bio]/Food and Nutrition ,Hyperinsulinism ,hormones, hormone substitutes, and hormone antagonists - Abstract
We investigated the effects of insulin and glucose on the control of secretion and gene expression of glucagon in vivo in rats. Animals were studied during 1) a 48-h period of either glucose infusion (hyperglycemia plus hyperinsulinemia; HG-HI rats) or insulin infusion (euglycemia plus hyperinsulinemia; EG-HI rats), and 2) a prolonged postinfusion period in both groups. In HG-HI rats, elevation of plasma insulin and glucose concentrations by about 7 and 5 times, respectively, resulted in a decline in glucagon levels, which fell significantly within 6 h and remained low thereafter, whereas these levels were unchanged in EG-HI rats. Glucagon messenger RNA levels and pancreatic glucagon content were not significantly affected in either HG-HI or EG-HI rats. After cessation of infusions, hypoglycemia occurred in both group of rats. In HG-HI rats, hypoglycemia lasted for about 36 h without any surge in the plasma glucagon level, whereas in EG-HI rats it was transient (approximately 1 h) and stimulated glucagon secretion. In both groups the pancreatic alpha-cell was unresponsive to arginine during the postinfusion period. In conclusion, although a role of intraislet insulin cannot be excluded, glucagon gene expression is insensitive to changes in plasma glucose and insulin concentrations. In contrast, hyperglycemia/hyperinsulinemia, not hyperinsulinemia alone, lowers glucagon secretion and affects the alpha-cell responsiveness to hypoglycemia.
- Published
- 1995
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