Neonatal energy metabolism in calves has to adapt to extrauterine life and depends on colostrum feeding. The adrenergic and glucocorticoid systems are involved in postnatal maturation of pathways related to energy metabolism and calves show elevated plasma concentrations of cortisol and catecholamines during perinatal life. We tested the hypothesis that hepatic glucocorticoid receptors (GR) and α 1 -and β 2 -adrenergic receptors (AR) in neonatal calves are involved in adaptation of postnatal energy metabolism and that respective binding capacities depend on colostrum feeding. Calves were fed colostrum (CF; n = 7) or a milk-based formula (FF; n = 7) with similar nutrient content up to d 4 of life. Blood samples were taken daily before feeding and 2 h after feeding on d 4 of life to measure metabolites and hormones related to energy metabolism in blood plasma. Liver tissue was obtained 2 h after feeding on d 4 to measure hepatic fat content and binding capacity of AR and GR. Maximal binding capacity and binding affinity were calculated by saturation binding assays using [3 H]-prazosin and [ 3 H]-CGP-12177 for determination of α 1 -and β 2 -AR and [ 3 H]-dexamethasone for determination of GR in liver. Additional liver samples were taken to measure mRNA abundance of AR and GR, and of key enzymes related to hepatic glucose and lipid metabolism. Plasma concentrations of albumin, triacylglycerides, insulin-like growth factor I, leptin, and thyroid hormones changed until d 4 and all these variables except leptin and thyroid hormones responded to feed intake on d 4. Diet effects were determined for albumin, insulin-like growth factor I, leptin, and thyroid hormones. Binding capacity for GR was greater and for α 1 -AR tended to be greater in CF than in FF calves. Binding affinities were in the same range for each receptor type. Gene expression of α 1 -AR (ADRA1) tended to be lower in CF than FF calves. Binding capacity of GR was related to parameters of glucose and lipid metabolism, whereas β 2 -AR binding capacity was negatively associated with glucose metabolism. In conclusion, our results indicate a dependence of GR and α 1 -AR on milk feeding immediately after birth and point to an involvement of hepatic GR and AR in postnatal adaptation of glucose and lipid metabolism in calves.

Catecholamines and glucocorticoids are involved in fetal maturation of organ systems to prepare the fetus for extrauterine life. Calves, especially when born preterm, depend on function of the adrenergic system and the glucocorticoid axis to adapt energy metabolism for the neonatal period. We tested the hypothesis that hepatic glucocorticoid and α1- and β2-adrenergic receptors in neonatal calves are involved in adaptation of energy metabolism around birth and that respective binding capacities depend on stage of maturation during the neonatal period. Calves (n=7 per group) were delivered by section preterm (PT, 9d before term) or were born at term (full-term, FT; spontaneous vaginal delivery), or spontaneously born and fed colostrum for 4d (FTC). Blood samples were taken immediately after birth and before and 2h after feeding at 24h after birth (PT, FT) or on d 4 of life (FTC) to determine metabolic and endocrine changes. After slaughter at 26h after birth (PT, FT) or on d 4 of life (FTC), liver tissue was obtained to measure hepatic binding capacity of glucocorticoid and α1- and β2-adrenergic receptors. Maximal binding capacity and binding affinity were calculated by saturation binding assays using [(3)H]-prazosin and [(3)H]-CGP-12177 for determination of α1- and β2-adrenergic receptors, respectively, and [(3)H]-dexamethasone for determination of glucocorticoid receptor in liver. Additional liver samples were taken to measure mRNA abundance of glucocorticoid and α1- and β2-adrenergic receptors, of key enzymes and factors related to hepatic lipid metabolism, and of insulin-like growth factor 1 (IGF1). Plasma concentrations of β-hydroxybutyrate and leptin changed with time, and leptin concentrations were affected by stage of maturation. The binding capacities for hepatic glucocorticoid and β2-adrenergic receptors as well as gene expression of IGF1 were greater in FTC than in FT and PT, and binding affinity for β2-adrenergic receptor was lowest in PT. The binding capacity of hepatic α1-adrenergic receptor was greatest in FTC and greater in FT than in PT. The binding capacities of glucocorticoid and α1-adrenergic receptors were mainly related to variables of glucose and lipid metabolism. In conclusion, our results indicate dependence of hepatic glucocorticoid and adrenergic receptors on stage of maturation in neonatal calves and emphasize the association of α1-adrenergic receptor and glucocorticoid receptor with neonatal glucose and lipid metabolism.