title: Identification of functional prolactin (PRL) receptor gene expression: PRL inhibits lipoprotein lipase activity in human white adipose tissue.
abstract: During lactation serum levels of prolactin (PRL) are elevated, and the activity of lipoprotein lipase (LPL) is decreased in the adipose tissue and increased in the mammary gland. However, PRL has been suggested to affect the adipose tissue in an indirect fashion during lactation. In the present study, we demonstrated expression of four PRL receptor (PRLR) mRNA isoforms (L, I, S1(a), and S1(b)) in human sc abdominal adipose tissue and breast adipose tissue using RT-PCR/Southern blot analysis. In addition, L-PRLR [relative molecular mass (M(r)) 90,000] and I-PRLR (M(r) 50,000) protein expression was detected in human sc abdominal adipose tissue and breast adipose tissue using immunoblot analysis. Two additional protein bands with the molecular weight M(r) 40-35,000 were also detected. The direct effect of PRL on the regulation of LPL activity in human abdominal adipose tissue cultured in vitro was investigated. PRL (500 ng/ml) reduced the LPL activity in human adipose tissue to 31 +/- 7.7%, compared with control. GH (100 ng/ml) also reduced the LPL activity, to 45 +/- 8.6%, compared with control. In agreement with previous studies, cortisol increased the LPL activity and GH inhibited cortisol-induced LPL activity. Furthermore, we found that PRL also inhibited the cortisol-induced LPL activity. Taken together, these results demonstrate a direct effect of PRL, via functional PRLRs, in reducing the LPL activity in human adipose tissue, and these results suggest that LPL might also be regulated in this fashion during lactation.
authors.affiliation: Department of Physiology, Sahlgrenska University Hospital, Göteborg University, 405 30 Göteborg, Sweden.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Ling
authors.forename: Louise
authors.initials: L
authors.lastname: Svensson
authors.forename: Birgitta
authors.initials: B
authors.lastname: Odén
authors.forename: Birgitta
authors.initials: B
authors.lastname: Weijdegård
authors.forename: Barbro
authors.initials: B
authors.lastname: Edén
authors.forename: Staffan
authors.initials: S
authors.lastname: Edén
authors.forename: Håkan
authors.initials: H
authors.lastname: Billig
mesh_terms: D000005:Abdomen; D000273:Adipose Tissue / Q000201:enzymology*; D000293:Adolescent; D000328:Adult; D001940:Breast; D046508:Culture Techniques; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D015870:Gene Expression; D006801:Humans; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors*; D008875:Middle Aged; D011388:Prolactin / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D011981:Receptors, Prolactin / Q000235:genetics*
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D011981:Receptors, Prolactin; D011388:Prolactin; D008071:Lipoprotein Lipase