TY - JOUR
T1 - Distinct placental lactogen and prolactin (lactogen) receptors in bovine endometrium
AU - Galosy, Sybille S.
AU - Gertler, Arieh
AU - Elberg, Gerard
AU - Laird, Don M.
PY - 1991/7
Y1 - 1991/7
N2 - Specific binding sites for bovine placental lactogen (bPL) and the lactogenic hormone, prolactin, have been detected in endometrial membranes isolated from uteri of mid-pregnant heifers. The specific binding of human growth hormone (hGH) (used to monitor the presence of lactogenic binding sites) and of bPL was increased approximately 4-fold following treatment of the membranes with 4 M MgCl2. Binding was found to be ligand specific, membrane protein concentration-, time- and temperature-dependent and reversible. Scatchard analysis of bPL and hGH competition binding data revealed curvilinear plots with dissociation constants for the high affinity sites of 4.1 × 10-11 M and 6.4 × 10-11 M, respectively. The maximum capacity of binding of bPL at the high affinity site was 21 fmol/mg membrane protein while approximately twice the level of binding was measured for hGH (39 fmol/mg). Both hGH and bGH, but not ovine prolactin, competed with [125I]bPL for binding. The concentrations of hGH and bGH needed to effectively compete were however 100-fold higher than those required for unlabeled bPL. No specific binding of radiolabeled bGH was detected in endometrial tissue suggesting the absence of bGH receptors. Preferential competition of [125I]hGH binding was observed by prolactin and bPL. From these data it may be inferred that hGH binding is indicative of the presence of both lactogenic (prolactin) and bPL binding sites in endometrial tissue. The presence of distinct bPL receptors in the endometrium from mid-pregnant cows suggests a possible role for bPL in the maintenance of pregnancy.
AB - Specific binding sites for bovine placental lactogen (bPL) and the lactogenic hormone, prolactin, have been detected in endometrial membranes isolated from uteri of mid-pregnant heifers. The specific binding of human growth hormone (hGH) (used to monitor the presence of lactogenic binding sites) and of bPL was increased approximately 4-fold following treatment of the membranes with 4 M MgCl2. Binding was found to be ligand specific, membrane protein concentration-, time- and temperature-dependent and reversible. Scatchard analysis of bPL and hGH competition binding data revealed curvilinear plots with dissociation constants for the high affinity sites of 4.1 × 10-11 M and 6.4 × 10-11 M, respectively. The maximum capacity of binding of bPL at the high affinity site was 21 fmol/mg membrane protein while approximately twice the level of binding was measured for hGH (39 fmol/mg). Both hGH and bGH, but not ovine prolactin, competed with [125I]bPL for binding. The concentrations of hGH and bGH needed to effectively compete were however 100-fold higher than those required for unlabeled bPL. No specific binding of radiolabeled bGH was detected in endometrial tissue suggesting the absence of bGH receptors. Preferential competition of [125I]hGH binding was observed by prolactin and bPL. From these data it may be inferred that hGH binding is indicative of the presence of both lactogenic (prolactin) and bPL binding sites in endometrial tissue. The presence of distinct bPL receptors in the endometrium from mid-pregnant cows suggests a possible role for bPL in the maintenance of pregnancy.
KW - (Bovine)
KW - Endometrium
KW - Placental lactogen receptor
UR - http://www.scopus.com/inward/record.url?scp=0025827975&partnerID=8YFLogxK
U2 - 10.1016/0303-7207(91)90127-E
DO - 10.1016/0303-7207(91)90127-E
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C2 - 1663880
AN - SCOPUS:0025827975
SN - 0303-7207
VL - 78
SP - 229
EP - 236
JO - Molecular and Cellular Endocrinology
JF - Molecular and Cellular Endocrinology
IS - 3
ER -