title: Effects of the rate of insulin infusion during isoglycemic, hyperinsulinemic clamp procedures on measures of insulin action in healthy, mature thoroughbred mares.
abstract: The objective of this study was to determine whether the rate of insulin infusion during isoglycemic hyperinsulinemic clamp procedures affected measures of insulin action, including glucose disposal and plasma non-esterified fatty acid, endothelin-1, and nitric oxide concentrations, in mature, healthy horses. Eight thoroughbred mares were studied during a 2-h hyperinsulinemic clamp procedure, conducted at each of 4 rates of insulin infusion: 0 (CON), 1.2 (LOWINS), 3 (MEDINS), and 6 (HIGHINS) mU · kg(-1) · min(-1). The infusion rate of a dextrose solution was adjusted throughout the clamp procedures to maintain blood glucose levels within 10% of baseline glucose concentrations. Plasma insulin concentrations were measured throughout the clamp procedures, and used with the rate of glucose infusion to calculate the plasma insulin concentration-to-rate of glucose infusion ratio, a measure of insulin action on glucose disposal. The rate of glucose infusion increased with rate of insulin infusion (P < 0.05). The plasma insulin concentration-to-rate of glucose infusion ratio was highest for the LOWINS treatment (P < 0.05) and decreased by 62% (P < 0.05) and 84% (P < 0.05) for the MEDINS and HIGHINS treatments, respectively. Although plasma non-esterified fatty acid concentrations were lower than baseline by t = 30 min of the clamp procedures in the LOWINS, MEDINS, and HIGHINS treatments (P < 0.05), the decline was similar for all 3 rates of insulin infusion. Jugular vein plasma nitric oxide and endothelin-1 concentrations were not affected by insulin infusion rate (P > 0.05). The data indicate that it is important to standardize insulin infusion rate if data are to be compared between hyperinsulinemic clamp studies.
authors: Middleburg Agricultural Research and Extension Center, Middleburg, VA 20117, USA; Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address: klur222@uky.edu.
authors: K L
authors: KL
authors: Urschel
authors: Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA.
authors: J
authors: J
authors: Escobar
authors: Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA 24061, USA; Marion duPont Scott Equine Medical Center, Virginia Tech, Leesburg, VA 20177, USA.
authors: L J
authors: LJ
authors: McCutcheon
authors: Middleburg Agricultural Research and Extension Center, Middleburg, VA 20117, USA; Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA.
authors: R J
authors: RJ
authors: Geor
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects* / Q000502:physiology; D018592:Cross-Over Studies; D005260:Female; D015309:Glucose Clamp Technique / Q000662:veterinary*; D006736:Horses / Q000502:physiology*; D007328:Insulin / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D007328:Insulin
keywords: Equine; Hyperinsulinemia; Hyperinsulinemic clamp; Insulin resistance