title: Novel role of insulin in the regulation of glucose excretion by mourning doves (Zenaida macroura).
abstract: In mammals, insulin primarily lowers plasma glucose (PGlu) by increasing its uptake into tissues. Studies have also shown that insulin lowers PGluin mammals by modulating glomerular filtration rate (GFR). Birds have naturally high PGluand, although insulin administration significantly decreases glucose concentrations, birds are resistant to insulin-mediated glucose uptake into tissues. Since prior work has not examined the effects of insulin on GFR in birds, the purpose of the present study was to assess whether insulin can augment renal glucose excretion and thereby lower PGlu. Therefore, the hypothesis of the present study was that insulin lowers PGluin birds by augmenting GFR, as estimated by inulin clearance (CIn). Adult mourning doves (Zenaida macroura) were used as experimental animals. Doves were anesthetized and the brachial vein was cannulated for administration of [14C]-inulin and insulin and the brachial artery was cannulated for blood collections. Ureteral urine was collected via a catheter inserted into the cloaca. Ten minutes following administration of exogenous insulin (400μg/kg body mass, i.v.) plasma glucose was significantly decreased (p=0.0003). Twenty minutes following insulin administration, increases in GFR (p=0.016) were observed along with decreases in urine glucose concentrations (p=0.008), glucose excretion (p=0.028), and the fractional excretion of glucose (p=0.003). Urine flow rate (p=0.051) also tended to increase after administration of insulin. These data demonstrate a significant role for insulin in modulating GFR in mourning doves, which may in part explain the lower PGlumeasured following insulin administration.
authors.affiliation: School of Nutrition and Health Promotion, Arizona State University, 550 North 3rd Street, Phoenix, AZ 85004, USA; School of Life Sciences, Arizona State University, 427 E Tyler Mall, Tempe, AZ 85287, USA. Electronic address: Karen.Sweazea@asu.edu.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Sweazea
authors.affiliation: Department of Physiology, College of Medicine, Arizona Health Sciences Center, University of Arizona, 1501 N. Campbell, Tucson, AZ 85724, USA.
authors.forename: Eldon J
authors.initials: EJ
authors.lastname: Braun
authors.affiliation: School of Nutrition and Health Promotion, Arizona State University, 550 North 3rd Street, Phoenix, AZ 85004, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Sparr
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D046092:Columbiformes / Q000378:metabolism*; D005919:Glomerular Filtration Rate / Q000187:drug effects / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D007444:Inulin
chemical_list: D001786:Blood Glucose; D007328:Insulin; D007444:Inulin; D005947:Glucose
keywords: Avian physiology; Glomerular filtration rate; Glucose excretion; Insulin metabolism; Kidney