title: Interaction of mouse prolactin with mouse hepatic receptors.
abstract: Lactogenic receptors are usually studied in heterologous systems where prolactin is derived from one species and receptors prepared from another. In such systems the foreign prolactin could be seen as a growth hormone by the host tissue. We have therefore developed a homologous radioreceptor assay using secreted mouse prolactin (smPRL) and mouse hepatic receptors. In this system, monovalent anions augment the smPRL-receptor interaction in the order F- greater than Cl- greater than Br- greater than I-. Divalent cations (Mg2+, Ca2+, Sr2+), phosphate and acetate also increase smPRL binding. Temperature and pH optima are at 8 degrees C and pH 8.3, respectively. Under optimum conditions, the percent total, specific and nonspecific binding are 55%, 45% and 10%, respectively. At infinite receptor concentration the maximum specific bindability of labeled smPRL is 50%. The effects of ions on binding of smPRL to the receptor show that hydrophobic forces participate in smPRL-receptor coupling. The biphasic dissociation kinetics show initial and final rate constants of 1.56 X 10(-4)/s and 7.62 X 10(-6)/s, respectively. The lactogenic receptor does not bind mouse growth hormone; however, it binds both mouse placental lactogen (mPL) and smPRL with equilibrium association constants of 3.90 X 10(8) M-1 and 2.25 X 10(8) M-1, respectively, suggesting that smPRL and mPL share biological roles by acting through the same receptor.
authors.forename: L S
authors.initials: LS
authors.lastname: Haro
authors.forename: F J
authors.initials: FJ
authors.lastname: Talamantes
mesh_terms: D000818:Animals; D000838:Anions; D002413:Cations, Divalent; D005260:Female; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D051379:Mice; D011247:Pregnancy; D011388:Prolactin / Q000378:metabolism*; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D011981:Receptors, Prolactin; D013045:Species Specificity; D013696:Temperature
chemical_list: D000838:Anions; D002413:Cations, Divalent; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D011981:Receptors, Prolactin; D011388:Prolactin