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

Abstract

During the switch from parenteral to enteral nutrition at birth, endocrine glands such as the pancreas must assume a glucoregulatory role for the first time if the neonate is to survive the transition to extrauterine life. To determine the adaptations in pancreatic endocrine function during the neonatal period in term pony foals delivered by different methods. By measuring insulin and glucagon concentrations, pancreatic alpha and beta cell responses to exogenous glucose (0.5 g/kg bwt) and arginine (100 mg/kg bwt) and to endogenous muzzling for 90 min were determined periodically over the first 10 post natal days in foals born spontaneously (n = 8) or by induction of labour with oxytocin at term (n = 7). Pancreatic alpha and beta cell function changed with post natal age in a manner related to the method of delivery. Induced foals had 2-3 fold greater beta cell responses to exogenous glucose and arginine, despite similar glucose and alpha-amino nitrogen clearances compared with spontaneously delivered foals. Pancreatic beta cell responses to glucose decreased by 50% while those to arginine doubled with increasing age in induced but not spontaneously delivered foals. In contrast, pancreatic alpha cell responses to arginine doubled with increasing age in foals born spontaneously but not by induction. These differences in pancreatic endocrine cell function with delivery method were associated with 2-3 fold higher cortisol levels in the induced foals and with differences in the absolute and age-related changes in basal concentrations of glucose, alpha-amino nitrogen and insulin. Induced delivery leads to changes in pancreatic beta cell sensitivity to glucose and/or tissue insulin resistance in association with persistent neonatal hypercortisolaemia. The altered post natal development of pancreatic endocrine function with induced delivery may compromise glucoregulation and adaptation to enteral nutrition in neonatal foals with potential consequences long after birth.