Effect of postnatal age and a β3-adrenergic agonist (Zeneca D7114) administration on uncoupling protein-1 abundance in the lamb
|J. A. Bird a1, A. Mostyn a4, L. Clarke a2, D. T. Juniper a3, H. Budge a4, T. Stephenson a4 and M. E. Symonds a4|
a4 Academic Division of Child Health, School of Human Development, University Hospital, Queen's Medical Centre, Nottingham NG7 2UH, a1 The Nightingale Institute, Division of Nursing and Midwifery, School of Life, Basic and Medical Health Sciences, Kings College, London SE1 9RT, a2 Department of Agriculture and Horticulture, Wye College, University of London, Wye, Ashford TN25 5AH and a3 Department of Agriculture, University of Reading, Reading RG 6 6AJ, UK
We examined the effect of time after birth and β3-adrenergic agonist (Zeneca D7114) administration on uncoupling protein-1 (UCP1) abundance and thermoregulation in the lamb. Forty twin lambs, all born normally at term, were maintained at a cold ambient temperature of between 3 and 8 °C. At 0.5, 1.75, 5.25, 11.25 and 23.25 h after birth eight sets of twins were fed 20 ml of formula milk ± 10 mg kg-1 of β3-adrenergic agonist, and 45 min after feeding brown adipose tissue (BAT) was sampled. Colonic temperature was measured and BAT analysed for UCP1 abundance, GDP-binding to mitochondrial protein (i.e. thermogenic activity) and catecholamine content. Colonic temperature declined between 1.25 and 6 h from 40.2 °C to 39.2 °C and then increased to 39.8 °C at 12 h, but increased after feeding at all ages. UCP1 abundance increased from 1.25 h after birth, to peak at 2 h after birth in controls, compared with 6 h after birth in β3-adrenergic agonist-treated lambs. The level of GDP-binding to mitochondrial protein did not change significantly with age but was increased by β3-adrenergic agonist treatment. The noradrenaline (norepinephrine) content of BAT increased between 1.25 and 12 h after birth, irrespective of β3-adrenergic agonist administration. The total weight of perirenal BAT plus its lipid, protein and mitochondrial protein content declined over the first 6 h of life. UCP1 development continues over the first 24 h of neonatal life, and can be manipulated by β3-adrenergic agonist administration. This may represent one method of improving thermoregulation in newborn lambs. Experimental
Physiology (2001) 86.1, 65-70.
(Received April 7 2000)
(Accepted December 1 2000)