Presented at the Neonatal Society 2002 Summer Meeting.
Hyatt M, Bispham J, Dandrea J, Walker D, Symonds ME, Stephenson T
Academic Division of Child Health, School of Human Development, University Hospital, Nottingham NG9 2UH
Introduction: Maternal nutrition during late-gestation may influence neonatal growth by altering maturation of the hypothalamo-pituitary-adrenal axis (1). Circulating PRL levels and PRLR abundance normally peak near to term (2). However, the extent to which the long and short forms of PRL receptor are nutritionally regulated in hepatic tissue remains to be determined.
Methods: Fourteen primiparous twin pregnant Border Leicester cross Swaledale ewes were entered into the study. Six ewes were allocated to the control (C) group and consumed 100% of total metabolisable energy (ME) requirements (for both ewe maintenance and growth of the conceptus in order to produce a 4.5 kg lamb at term). The remaining eight ewes were nutrient restricted (NR) and consumed 60% of total ME requirements. All ewes lambed normally at term, and one twin was euthanased with an overdose of barbiturate (100 mg kg-1 pentobarbital sodium: Euthatal) within 6 h of birth to enable liver sampling with the remaining twin being reared with its ewe until 30 d after birth. Total RNA was extracted from the liver, reverse transcribed and abundance of PRLR measured by polymerase chain reaction of reverse transcribed product using oligonucleotide primers specific to the long and short forms of PRLR (3). Results are given as means with their standard errors in arbitrary units (a.u) as a ratio of 18S rRNA and are expressed as a percentage of a reference sample present on all gels. Differences in nutritional treatments were analysed using a Mann-Whitney U-test.
Results:
Significantly different from control at * P<0.05 level, as measured by Mann-Whitney U-test.
Conclusion: Maternal nutrient restriction over the final month of gestation resulted in lower hepatic mRNA abundance for both long and short forms of PRLR at birth and 30 d of postnatal age. This difference was only significant at birth for the short form of PRLR. Downregulation of PRLR mRNA occurred in the absence of any significant difference in lamb or liver weights, but may contribute to significant alterations in later growth and metabolic function.
References
1. Edwards LJ Symonds ME, Warnes KE, Owens JA, Butler TG, Jurisevic A & McMillen IC (2001) Endocrinology 142, 1778-1785.
2. Phillips ID, Anthony RV, Butler TG, Ross JT, McMillen IC (1997) Endocrinology 138, 1351-1354.
3. Nixon AJ, Ford CA, Wildermoth JE, Craven AJ, Ashby MG & Pearson AJ (2002) J. Endocrinol. 172, 605-614.