Identification of multiple low molecular weight placental prolactin-like proteins produced by rat trophoblast cells.
Rat trophoblast tissue was found to synthesize a number of low molecular weight proteins possessing prolactin-like characteristics. There appear to be at least three proteins that cross-react with antisera to pituitary prolactin. Two of the proteins had a molecular weight of 25,000, similar to ovine pituitary prolactin, and isoelectric points of 6.8 and 7.0. The third immunoreactive protein had a lower molecular weight (23,500), similar in size to human placental lactogen, and a slightly more acidic isoelectric point of 6.75. The molecular weight variants cross-reacted with an antipeptide serum that was generated to a synthetic peptide representing amino acids 150 to 164 of rat placental lactogen-2 (PL-2). Based on this analysis, we consider these proteins to be related to PL-2. Analysis of trophoblast proteins by gel-filtration chromatography resulted in the identification of another trophoblast prolactin. This material eluted earlier than PL-2-related proteins on a gel-filtration column, possessed prolactin-like activity (determined by competition with ovine pituitary prolactin for rabbit mammary gland or rat liver prolactin receptors) but showed limited cross-reactivity with either the antiserum to pituitary prolactin or the antiserum to the PL-2 peptide. We have thus identified multiple low molecular weight trophoblast prolactins, possessing different biochemical and immunological characteristics.
Soares
M J
MJ
Department of Physiology, Ralph L. Smith Mental Retardation Research Center, University of Kansas Medical Center, Kansas City 66103.
De
S K
SK
Foster
B A
BA
Julian
J A
JA
Glasser
S R
SR
D000818:Animals; D002478:Cells, Cultured; D003429:Cross Reactions; D005260:Female; D008970:Molecular Weight; D010926:Placental Hormones / Q000302:isolation & purification*; D051381:Rats; D011981:Receptors, Prolactin / Q000378:metabolism; D014327:Trophoblasts / Q000032:analysis* / Q000166:cytology
D010926:Placental Hormones; D011981:Receptors, Prolactin