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Diminished epinephrine response to hypoglycemia despite enlarged adrenal medulla in trained rats. 1990

B Stallknecht, and M Kjaer, and K J Mikines, and L Maroun, and T Ploug, and T Ohkuwa, and J Vinten, and H Galbo
Department of Medical Physiology B, Panum Institute, University of Copenhagen, Denmark.

Studies in humans have indicated that trained athletes compared with sedentary subjects have an increased capacity to secrete epinephrine. To investigate whether this is due to an adaptation induced by physical training or a selection phenomenon, rats were swim trained (T) 10 wk for 6 h/day or served as controls being either sedentary freely eating (C), food restricted (FR), sham swim trained (ST), or cold stressed (CS). Adrenal glands were weighted and cross sectioned for light microscopic determination of size of the adrenal medulla. Endurance-trained compared with control rats had heavier adrenal glands (P less than 0.05), higher catecholamine content in the glands (P less than 0.05), and higher adrenal medulla volumes (P less than 0.05) [males: 2.74 +/- 0.16 (T) vs. 2.05 +/- 0.16 (C), 1.90 +/- 0.10 (ST), and 2.21 +/- 0.08 mm3 (CS)] [females: 2.55 +/- 0.11 (T) vs. 1.92 +/- 0.06 mm3 (C)]. Cold stress or sham swim training did not increase adrenal weight or volume of adrenal medulla (P greater than 0.05). To stimulate adrenal medulla secretion, rats had an insulin-induced hypoglycemia. Insulin dose needed to suppress plasma glucose below 4.0 mM was four times greater in sedentary compared with trained rats. During hypoglycemia the epinephrine response was much smaller in trained than in untrained rats (P less than 0.05). In conclusion, in rats strenuous endurance training causes an enlargement of the adrenal medulla. However, possibly reflecting an adaptation within the central nervous system to reduced blood glucose levels induced by repeated exercise bouts, the epinephrine response to insulin-induced hypoglycemia is markedly diminished after training.

UI MeSH Term Description Entries
D007003 Hypoglycemia A syndrome of abnormally low BLOOD GLUCOSE level. Clinical hypoglycemia has diverse etiologies. Severe hypoglycemia eventually lead to glucose deprivation of the CENTRAL NERVOUS SYSTEM resulting in HUNGER; SWEATING; PARESTHESIA; impaired mental function; SEIZURES; COMA; and even DEATH. Fasting Hypoglycemia,Postabsorptive Hypoglycemia,Postprandial Hypoglycemia,Reactive Hypoglycemia,Hypoglycemia, Fasting,Hypoglycemia, Postabsorptive,Hypoglycemia, Postprandial,Hypoglycemia, Reactive
D007328 Insulin A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1). Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D009638 Norepinephrine Precursor of epinephrine that is secreted by the ADRENAL MEDULLA and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the LOCUS CERULEUS. It is also found in plants and is used pharmacologically as a sympathomimetic. Levarterenol,Levonorepinephrine,Noradrenaline,Arterenol,Levonor,Levophed,Levophed Bitartrate,Noradrenaline Bitartrate,Noradrénaline tartrate renaudin,Norepinephrin d-Tartrate (1:1),Norepinephrine Bitartrate,Norepinephrine Hydrochloride,Norepinephrine Hydrochloride, (+)-Isomer,Norepinephrine Hydrochloride, (+,-)-Isomer,Norepinephrine d-Tartrate (1:1),Norepinephrine l-Tartrate (1:1),Norepinephrine l-Tartrate (1:1), (+,-)-Isomer,Norepinephrine l-Tartrate (1:1), Monohydrate,Norepinephrine l-Tartrate (1:1), Monohydrate, (+)-Isomer,Norepinephrine l-Tartrate (1:2),Norepinephrine l-Tartrate, (+)-Isomer,Norepinephrine, (+)-Isomer,Norepinephrine, (+,-)-Isomer
D010805 Physical Conditioning, Animal Diet modification and physical exercise to improve the ability of animals to perform physical activities. Animal Physical Conditioning,Animal Physical Conditionings,Conditioning, Animal Physical,Conditionings, Animal Physical,Physical Conditionings, Animal
D011919 Rats, Inbred Strains Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding. August Rats,Inbred Rat Strains,Inbred Strain of Rat,Inbred Strain of Rats,Inbred Strains of Rats,Rat, Inbred Strain,August Rat,Inbred Rat Strain,Inbred Strain Rat,Inbred Strain Rats,Inbred Strains Rat,Inbred Strains Rats,Rat Inbred Strain,Rat Inbred Strains,Rat Strain, Inbred,Rat Strains, Inbred,Rat, August,Rat, Inbred Strains,Rats Inbred Strain,Rats Inbred Strains,Rats, August,Rats, Inbred Strain,Strain Rat, Inbred,Strain Rats, Inbred,Strain, Inbred Rat,Strains, Inbred Rat
D001786 Blood Glucose Glucose in blood. Blood Sugar,Glucose, Blood,Sugar, Blood
D004837 Epinephrine The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS. Adrenaline,4-(1-Hydroxy-2-(methylamino)ethyl)-1,2-benzenediol,Adrenaline Acid Tartrate,Adrenaline Bitartrate,Adrenaline Hydrochloride,Epifrin,Epinephrine Acetate,Epinephrine Bitartrate,Epinephrine Hydrochloride,Epinephrine Hydrogen Tartrate,Epitrate,Lyophrin,Medihaler-Epi,Acetate, Epinephrine
D005260 Female Females
D000313 Adrenal Medulla The inner portion of the adrenal gland. Derived from ECTODERM, adrenal medulla consists mainly of CHROMAFFIN CELLS that produces and stores a number of NEUROTRANSMITTERS, mainly adrenaline (EPINEPHRINE) and NOREPINEPHRINE. The activity of the adrenal medulla is regulated by the SYMPATHETIC NERVOUS SYSTEM. Adrenal Medullas,Medulla, Adrenal,Medullas, Adrenal
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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