Endocrine Abstracts

Introduction: In lambs, the rapid increase in heat production after birth is due to the initiation of nonshivering thermogenesis in brown adipose tissue (BAT). This occurs in conjunction with an increase in amount and activity of the BAT specific uncoupling protein 1 (UCP1). Both mRNA and protein for the long and short forms of the prolactin receptor are highly abundant in ovine BAT up to the time of birth. The following study aimed to determine whether prolactin administration to newborn lambs promotes thermoregulation.

Method: Seven pairs of day old triplet lambs were entered into the study and randomly assigned to prolactin (2mg/ml) or vehicle treatment. Treatment was administered to all lambs via the jugular vein. Colonic temperature was measured prior to treatment and then at ten-minute intervals for the next two hours. Then all lambs were humanely euthansed and perirenal adipose tissue was sampled for measurement of the abundance of UCP1. Blood samples were also taken and plasma concentration of non-esterified free fatty acid (NEFA) concentration determined. Values are means with their standard errors.

Results and Conclusion: There was no difference in colonic temperature between groups at the start of the study (vehicle 39.51 plus/minus 0.11 and prolactin treated 39.38 plus/minus 0.12 (degC)). However, there was a significant increase in the colonic temperature of the prolactin treated lambs compared to the control lambs 40 to 60 minutes after treatment. The concentration of NEFA was significantly increased after PRL treatment (vehicle delta 0.06 plus/minus 0.4 and PRL delta 0.23 plus/minus 0.4 nmol/litre (p=0.025)), which is likely to increase the thermogenic potential of UCP1. The effect of prolactin on thermoregulation was observed in the absence of shivering suggesting, that prolactin acting via its receptor promotes lipolysis and therefore nonshivering thermogenesis in BAT.

S.Pearce was supported by a BBSRC Postgraduate Studentship.