Presented at the Neonatal Society 2002 Spring Meeting.

Pearce S¹, Alves-Guerra MC², Pecqueur C², Miroux B², Symonds ME¹, Stephenson T¹

¹ Academic Division of Child Health, Queen’s Medical Centre, Nottingham NG7 2UH, UK
² CEREMOD, 9 rue Jules Hetzel, 92190 Meudon, France

Aims: Uncoupling protein 2 (UCP2), located on the inner mitochondrial membrane, and has been proposed to regulate reactive oxygen species production (Arsenijevic et al. 2000) although its function may depend on the stage of development. A close relationship between the ontogeny of both mRNA and protein for the long and short forms of the prolactin receptor (PRLR) and the initial appearance of UCP1 has been shown in fetal adipose tissue in late gestation (Symonds et al. 1998). The present study aimed to establish whether a similar association is present for UCP2 in the pregnant uterus.

Methods: Uterine myometrial samples (n=3 per stage of gestation) were taken from Bluefaced Leicester x Swaledale ewes at 85, 99, 114 and 131 days gestation (term = 148 days). Mitochondria were analysed using immunoblotting with an antibody specific for UCP2. Abundance of the long and short forms of PRLR were similarly determined in plasma membranes using antibodies specific to each form of PRLR (Budge et al. 2000).

Results: Results are expressed in arbitrary units (a.u.) as means with their standard errors.

There was a gradual increase in UCP2 abundance with gestation that peaked at 114 days gestation. This rise in UCP2 content was proceeded by a peak in both long and short forms of PRLR at 99 days gestation.

Conclusion: The rise in UCP2 with gestation within the pregnant uterus may be important in regulating uterine mitochondrial activity in late gestation as fetal growth and size becomes maximal. The concomitant rise in PRLR abundance prior to a peak in UCP2 is in accord with findings for PRLR and UCP1 in fetal adipose tissue. Taken together these findings indicate PRLR could be an important endocrine factor regulating the increase in UCP2 in uterine myometrium between mid to late gestation.

References
Symonds ME, Phillips ID, Anthony RV, Owens JA & McMillen IC (1998) Journal of Neuroendocrinology 10, 885- 890.
Arsenijevic D, Onuma H, Pecquer C, Raimbault S, Manning BS, Miroux B, Couplan E, Alves-Guerra M-C, Goubern M, Surwit R, Bouillaud F, Richard D, Collins S, Ricquier D. (2000) Nature Genetics 26: 435-439.
Budge H, Bispham J, Dandrea J, Evans L, Heasman L, Ingleton P, Sullivan C, Wilson V, Stephenson T, Symonds ME (2000) Pediatr. Res. 47, 781-786