title: Sex-associated differences in pancreatic β cell function in healthy preweaning pony foals.
abstract: BACKGROUND
  Pancreatic β cells are responsive to a range of stimuli during early post natal life in healthy pony foals. However, little is known about whether these responses are sex-linked.
  
  
  OBJECTIVE
  To determine pancreatic β cell responses to the insulin secretagogues, glucose, arginine and tolbutamide, in fillies and colts during the first 3 months after birth.
  
  
  METHODS
  In vivo experiment examining sex differences in pancreatic β cell function in foals.
  
  
  METHODS
  Female (n = 8) and male (n = 5) pony foals were infused i.v. with glucose (0.5 g/kg bwt 40% dextrose), arginine (100 mg/kg bwt) or tolbutamide (10 or 20 mg/kg bwt) over 5 min, at 48 h intervals, to assess pancreatic β cell function at ages 2 and 12 weeks. Blood samples (4 ml) were taken through a jugular catheter at -30, -15 and 0 min (immediately before) and 5, 15, 30, 45, 60, 90 and 120 min after glucose, arginine and tolbutamide administration for measurements of plasma glucose, α-amino-nitrogen and insulin concentrations.
  
  
  RESULTS
  The maximum increment in plasma insulin concentration in response to glucose was significantly higher in female (395 ± 58 ng/l) than male (172 ± 37 ng/l, P<0.05) pony foals 2 weeks after birth and the area under the insulin curve was significantly greater in females at this age. At 12 weeks, the insulin increment in response to glucose was significantly greater in fillies 45 min post infusion. The β cell responses to arginine and tolbutamide were not sex-linked at either age.
  
  
  CONCLUSIONS
  These data show that in ponies, fillies have a greater β cell response to glucose than colts in early post natal life. Since glucose clearance was unaffected by sex, the results suggest that fillies may be less insulin sensitive than colts shortly after birth. Innate sex differences in the secretion and action of insulin in early post natal life may influence tissue development and growth with potentially more long-term metabolic consequences.
authors.affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, UK.
authors.forename: J K
authors.initials: JK
authors.lastname: Jellyman
authors.forename: O A
authors.initials: OA
authors.lastname: Valenzuela
authors.forename: V L
authors.initials: VL
authors.lastname: Allen
authors.forename: N B
authors.initials: NB
authors.lastname: Holdstock
authors.forename: A L
authors.initials: AL
authors.lastname: Fowden
mesh_terms: D000818:Animals; D000833:Animals, Suckling / Q000502:physiology*; D001786:Blood Glucose; D005260:Female; D005947:Glucose / Q000378:metabolism; D006736:Horses / Q000502:physiology*; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000502:physiology*; D008297:Male; D012737:Sex Factors; D014044:Tolbutamide / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D014044:Tolbutamide; D005947:Glucose
keywords: foal; glucose; horse; insulin; metabolism; sex