Pancreatic α Cell Function in the Fetal Foal During Late Gestation

Abstract

summaryPlasma glucagon concentrations were measured in chronically catheterized fetal ponies and their mothers between 260 days of gestation and term ( 335 days). Fetal á cell responses to arginine and variations in fetal glycaemia were also examined during late gestation. Immunoreactive glucagon was present in fetal plasma at 260 days of gestation and its concentration in utero increased after 320 days and then again at birth. Maternal plasma glucagon concentrations were higher after 300 days than earlier in gestation but were lower than the corresponding fetal value throughout the period of gestation studied. Fetal á cells responded rapidly to intravenous arginine infusion but not to changes in the fetal glucose level induced by maternal fasting for 36 h or by intrafetal infusion of glucose. The maximal increment in fetal plasma glucagon in response to arginine occurred at the end of the 5 min infusion and was positively correlated to the basal preinfusion plasma glucagon concentrations. Fetal plasma glucagon concentrations were unaffected by either hyper-or hypoglycaemia. In contrast, maternal plasma glucagon levels were significantly increased by fasting. These observations indicate that equine pancreatic á

Pancreatic endocrine function in newborn pony foals after induced or spontaneous delivery at term

“…Compared to pancreatic β cells, much less is known about the ontogeny of α cell function during the nutritional transition at birth. Glucagon is detectable in fetal plasma during late gestation in a number of species and rises in concentration in fetal horses towards term to peak at delivery (Fowden et al . 1999; Fowden and Hill 2001).…”

“…Metabolite concentrations: Plasma glucose and α‐amino nitrogen concentrations were determined colorimetrically as described previously (Fowden et al . 1982, 1999).…”

Comparative aspects of prepartum maturation: Provision of nutrients

“…1: Arteriell plasma concentrations of cortisol, adrenaline, noradrenaline, insulin and glucagon in fetuses of different species at 95% of gestation ans at birth. Data from Fowden et al 1984Fowden et al , 1995bFowden et al , 1999Silver et al 1986Silver et al , 1987 Arterielle Plasmakonzentration von Kortison, Adrenalin, Noradrenalin, Insulin und Glucagon in Feten verschiedener Tierarten nach 95% der Trächtigkeit und zum Zeitpunkt der Geburt. Daten von Fowden et al 1984, 1995b, 1999Silver et al 1986Silver et al , 1987 Cortisol ng.ml -1…”

“…Both the set point and sensitivity of glucose-stimulated insulin secretion are therefore altered at birth . Similarly, the pancreatic α cell response to arginine increases in magnitude during late gestation in fetal sheep and horses (Aldoretta et al, 1998;Fowden et al, 1999). Basal circulating glucagon concentrations also rise during late gestation in fetal pigs, sheep and horses (Fowden et al, 1999;Fowden and Hill, 2001).…”

“…Similarly, the pancreatic α cell response to arginine increases in magnitude during late gestation in fetal sheep and horses (Aldoretta et al, 1998;Fowden et al, 1999). Basal circulating glucagon concentrations also rise during late gestation in fetal pigs, sheep and horses (Fowden et al, 1999;Fowden and Hill, 2001). In addition, innervation of the islets of Langerhans is completed during late gestation in most species (Fowden and Hill, 2001).…”