Prolactin and Brown Adipocytes Figure 1. Lack of PRLR impaired brown adipose tissue development in newborns. A) Body weight (BW), BAT weight and BAT/BW ratio were determined in newborn wild type (WT) and PRLR (KO) mice. The BAT weight and BAT/BW ratio were significantly lower in PRLR KO mice (n = 16) than in WT animals (n = 15) (*p,0.05). Results represent mean6SE. B, C and D) Decreased brown adipocyte size in BAT of PRLR KO (C) compared to WT mice (B). BAT of newborn animals were collected, fixed and stained with hematoxylin and eosin. Representative images are presented (objective660). Adipocyte cell surface was calculated using the Lucia software and a significant decreased was detected in PRLR KO mice (n = 5) vs controls (n = 5) (***p,0.001, n = 200 cells /group). E) Intracellular triglyceride content of BAT was significantly reduced in PRLR KO mice (**p,0.01). F, G and H) Drastic decrease of PPARc2, SREBP1 and PGC-1a mRNA expression in BAT of PRLR KO mice compared to control littermates. BAT of WT and PRLR KO newborn mice were collected, total RNA extracted and processed for quantitative real time PCR analysis of gene expression as described in the Materials and Methods section. Relative expression within a given sample was calculated as the ratio (attomol of specific gene/fmol of 18S). Results are presented as mean6SE of 15–16 animals. * p,0.05 and ** p,0.01. doi:10.1371/journal.pone.0001535.g001 PLoS ONE | www.plosone.org 3 February 2008 | Issue 2 | e1535