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At least 19 recordsLinked to original sources
PubMed1990

Purification, partial characterization, and development of a specific radioimmunoassay for goat placental lactogen.

Placental lactogen (PL) was isolated from goat cotyledonary tissue by a combination of mild alkaline extraction, anion and cation exchange chromatography, chromatofocussing and molecular filtration. The product, enriched 15,000-fold from the initial extract, was homogeneous when examined by SDS-gel electrophoresis (Mr 22,500) and isoelectricfocussing indicated a pI of 8.35 with a trace contaminant of pI 8.0. When assessed by relative binding activity in radioreceptor assays (RRA), goat PL exhibited somatotropic activity equivalent to 2.2 units/mg dry weight and lactogenic activity equivalent to 28.5 units/mg. A radioimmunoassay (RIA) for goat PL is described that is highly sensitive (190 pg/tube) and has acceptable repeatability within and between assays (6 and 13%, respectively). The assay is not affected by goat pituitary extracts or partly purified goat growth hormone and prolactin. Despite the marked increase in sensitivity of the RIA over that previously available when goat PL was measured by RRA, the hormone was not detected in jugular plasma of goats before Day 44 of pregnancy; concentrations increased thereafter and highest levels were measured during the last third of pregnancy in animals bearing triplets. Measurements by RIA are in general agreement with those obtained earlier in several studies in which RRAs were used. The hormone was detected in amniotic fluid. Maternal concentrations of goat PL declined before parturition and were undetectable by 18 h post partum.

Animals↗
PubMed1994

The release of human chorionic gonadotrophin and placental lactogen by placental explants can be stimulated by Ca2+ entry through a Na(+)-Ca2+ exchange process.

Isosmotical replacement of extracellular Na+ ([Na+]o) by K+, choline and to a lesser extent by saccharose stimulated the release of chorionic gonadotrophin and placental lactogen from human term placental explants. The effect of [Na+]o removal on the release of both hormones was concentration-dependent and was inhibited in the absence of extracellular Ca2+ or in the presence of 0.5 mM Co2+, a Ca2+ entry blocker. Blockers of the voltage-sensitive Ca2+ channels (20 microM nifedipine and 50 microM methoxyverapamil) or Na+ channels (5 microM tetrodotoxin) did not affect the stimulatory effects of [Na+]o omission. By contrast, Mg2+ and Sr2+ (10 mM) as well as amiloride (2 mM) and its analogue 2',4'-dimethylbenzamil (50 microns), all known to affect the Na(+)-Ca2+ exchange, markedly reduced the increase in hormone release elicited by [Na+]o removal. Lastly, the secretory responses to [Na+]o deprivation were increased in the presence of 2 mM ouabain, an inhibitor of the Na(+)-K+ ATPase. These results indicate for the first time that [Na+]o omission provokes a Ca(2+)-dependent stimulation of human chorionic gonadotrophin and placental lactogen releases. The pharmacological dissection of the secretory effects of [Na+]o removal supports the existence of a process of Na(+)-Ca2+ exchange in placental cells.

Calcium↗
PubMed1975

Uptake of 125-I-labelled human placental lactogen and human placental lactogen by the tissues of normal and lactating rats.

The rate of clearance from the circulation and uptake into tissues of radioactive label was studied after i.v. injection of 125-I-labelled human placental lactogen (HPL) into rats at various stages of pregnancy. The half-life was obtained for the disappearance of the trichloroacetic acid-precipitable material from the plasma. The half-life, t1/2(S), calculated over the first 5 min after injection of the hormone was 5.4 equals or minus 1.1 (S.D.) min, while a half-life, t1/2(L), of 27.9 equals or minus 2.3 min was obtained from the decay period of 15-35 min. In the non-pregnant and pregnant rat the highest ratio of the radioactivity in an organ to that in the blood was 12-14:1 in the kidney. That the kidney is mainly involved in the uptake of exogenous HPL is further confirmed by the application of the histochemical immunoperoxidase technique. Human placental lactogen was localized in the cells of the proximal tubules of the cortex and to a lesser extent in the tubular lumen and the tubules of the medulla region. UPTAKE OF HPL in vivo occurs in the mammary gland tissue of the post-partum rat and reaches a maximum uptake between 15 and 30 min after injection of the hormone. Furthermore, specific uptake of HPL was observed on the alveolar cell membranes after the incubation of paraffin-embedded sections of formalin-fixed mammary gland and subsequent treatment by the peroxidase-labelled antibody method. These findings support the work of others who have demonstrated the presence of specific membrane receptors in the mammary gland for hormones with prolactin-like activity.

Absorption↗
PubMed1987

Immunocytochemical localization of chorionic gonadotropin, placental lactogen, and placental alkaline phosphatase in the diagnosis of complete and partial hydatidiform moles.

Complete hydatidiform moles (CHMs) and partial hydatidiform moles (PHMs) represent different clinicopathologic entities with characteristic morphologic and cytogenetic findings. In the absence of cytogenetic data, the histologic distinction between these lesions and abortuses showing hydropic swelling (AHS) may be difficult. An immunocytochemical study analyzing the distribution of human chorionic gonadotropin (hCG), human placental lactogen (hPL), and placental alkaline phosphatase (PlAP) in CHMs, PHMs, and AHS was undertaken to determine whether the expression of these trophoblastic proteins might assist in the differential diagnosis. A total of 24 CHMs, 22 PHMs, and 13 AHS were selected on the basis of established morphologic criteria. Thirty-four specimens of abortuses without hydropic swelling and normal placentas, ranging from 6 to 24 weeks gestational age, were similarly analyzed. The immunocytochemical localization of the three trophoblastic proteins, predominantly in syncytiotrophoblast (ST), was scored using a semiquantitative scoring system. In CHMs hCG is widely distributed and PlAP is patchily distributed in ST regardless of the gestational age, whereas hPL tends to increase with increasing gestational age. In contrast, in PHMs hPL is more widely distributed in ST compared with CHMs regardless of gestational age, while PlAP increases with increasing gestational age; in PHMs the distribution of hCG is markedly less than in CHMs except early in the first trimester when the staining patterns are similar. The different patterns of distribution of hCG, hPL, and PlAP may reflect differences in the pathobiology of trophoblast in CHMs and PHMs and appear to be useful in the differential diagnosis of these conditions.

Abortion, Spontaneous↗
PubMed1994

Ca2+ entry through L-type voltage-sensitive Ca2+ channels stimulates the release of human chorionic gonadotrophin and placental lactogen by placental explants.

The release of human chorionic gonadotrophin (hCG) and placental lactogen (hPL) by human placental explants can be stimulated by Ca2+ entry. The aim of the present study was to characterize the modality of Ca2+ entry in the presence of high extracellular K+ concentration ([K+]o). A rise in [K+]o from 5 to > or = 50 mM induced a rapid and marked increase in the release of hCG and hPL from human term placental explants. The stimulatory effects of an excess [K+]o on the release of hCG and hPL were blocked in the absence of extracellular Ca2+ or in the presence of 0.5 mM Co2+. The presence of 50 microM methoxyverapamil, 20 microM nifedipine or 40 microM Cd2+ in the medium inhibited the stimulatory effects of [K+]o addition. Lastly, 40 microM Ni2+ failed to affect the increases in hCG and hPL releases elicited by [K+]o addition. Our data clearly show that a rise in [K+]o stimulates the release of hCG and hPL from placental explants. These secretory effects can be viewed as resulting from a Ca2+ entry through voltage-sensitive Ca2+ channels of the L-type.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1998

Absence of human placental lactogen and placental growth hormone (HGH-V) during pregnancy: PCR analysis of the deletion.

Human placental lactogen (HPL) is produced in large amounts in normal pregnancies. We report a pregnancy with complete lack of HPL and the placental variant of the human growth hormone HGH-V. The pregnancy resulted in a severely growth-retarded but otherwise normal male baby. PCR analysis of DNA extracted from the placenta showed that the HPL encoding genes hPL-4 and hPL-3 were deleted along with the human growth hormone variant gene (hGH-V), which is located between these two active hPL genes and also expressed in the normal placenta. Of the five members of this multigene family, hGH-N, which is expressed in the pituitary gland, and hPL-1, a presumed pseudogene, were left intact. The latter (hPL-1) was expressed as RNA transcripts only at very low levels as is usually reported in normal pregnancies. Analysis of the parents' DNA showed that both of them carried a different heterozygous deletion at the 3' end of the hGH/hPL locus.

Adult↗
PubMed1986

Sn-1,2-diacylglycerols and phorbol esters stimulate the synthesis and release of human placental lactogen from placental cells: a role for protein kinase C.

Activation of calcium-stimulated phospholipid-dependent protein kinase C (PKC) by diacylglycerols and phorbol esters has been shown to mediate the release of secretory proteins in several systems. To determine whether PKC activation is involved in regulation of the release of human placental lactogen (hPL) from the placenta, we examined the effects of various acylglycerols and phorbol esters on the release of hPL from cultured human trophoblast cells. Sn-1,2-dioctanoylglycerol (diC8) and phorbol-12-myristate-13-acetate (PMA), both of which stimulate placental protein kinase C activity, caused dose-dependent increases in hPL release over a 0.5-h period. The maximal amounts of hPL released in response to diC8 (300 microM) and PMA (10(-8) M) were 200-300% and 150-225% greater, respectively, than that released in response to diluent alone. Acylglycerols and phorbol esters, which are less potent stimulators of PKC activity in other systems, stimulated hPL release to a lesser extent than either diC8 or PMA. PKC-inactive acylglycerols and phorbol esters were without effect. After 0.5 h of exposure, diC8 (300 microM)- and PMA (10(-8) M)-exposed cells synthesized 257.5% and 250.3% more hPL than control cells. Cycloheximide at a dose (50 micrograms/ml) that inhibited the synthesis of trichloroacetic acid-precipitable [35S]methionyl placental proteins by more than 80% completely blocked the stimulatory effects of diC8 and PMA on hPL synthesis and release. Although diC8 and PMA stimulated the synthesis and release of hPL, these compounds had no effect on the release of hCG and did not cause the release of the cytosolic enzymes lactic dehydrogenase and alkaline phosphatase. The demonstration that acylglycerols and phorbol esters stimulate the synthesis and release of hPL strongly implicates protein kinase C activation in the mechanisms of hPL synthesis and release.

Cycloheximide↗
PubMed1991

Relations between maternal and fetal plasma concentrations of placental lactogen and placental and fetal weights in well-fed ewes.

The concentration of ovine placental lactogen (oPL) in maternal plasma varies with litter size and nutritional status, making it difficult to compare these concentrations across studies. In this study, 27 Dorset and Finn-Dorset crossbred ewes with litters of known size and gestational age were used to relate concentrations of oPL in maternal plasma to placental and fetal weights. Fetal oPL concentrations also were correlated to these variables in 12 chronically catheterized singleton fetuses. The concentration of oPL in maternal plasma increased with increasing placental weight across litter sizes ranging from 1 to 3 (r = .716). When expressed per gram of placenta, oPL was greater (P less than .05) in those ewes carrying multiple fetuses. There was no correlation between maternal and fetal oPL in time-matched samples or in average values between individuals for ewes carrying singleton pregnancies. Within the singleton group, placental weight and fetal weight were well correlated (r = .761), as were the concentration of fetal plasma oPL and fetal weight (r = .699). Placental weight plus fetal oPL could explain 81% of the variation seen in fetal weight. These results imply that maternal and fetal oPL release are controlled independently and that fetal oPL affects fetal growth by a mechanism not directly related to placental size.

Animals↗
PubMed2004

Characterization of mice doubly transgenic for parathyroid hormone-related protein and murine placental lactogen: a novel role for placental lactogen in pancreatic beta-cell survival.

Transgenic overexpression of either parathyroid hormone-related peptide (PTHrP) or mouse placental lactogen type 1 (mPL1) in pancreatic beta-cells, using the rat insulin II promoter (RIP), results in islet hyperplasia either through prolonged beta-cell survival or through increased beta-cell proliferation and hypertrophy, respectively. For determining whether the two proteins might exert complementary, additive, or synergistic effects on islet mass and function when simultaneously overexpressed in beta-cells in vivo, RIP-PTHrP and RIP-mPL1 mice were crossed to generate mice doubly transgenic for PTHrP and mPL1. These double-transgenic mice displayed marked islet hyperplasia (threefold), hypoglycemia, increased beta-cell proliferation (threefold), and resistance to the diabetogenic and cytotoxic effects of streptozotocin compared with their normal siblings. Although the phenotype of the double-transgenic mice was neither additive nor synergistic relative to their single-transgenic counterparts, it was indeed complementary, yielding the maximal salutary phenotypic features of both individual transgenes. Finally, mPL1, for the first time, was shown to exert a protective effect on the survival of beta-cells, placing it among the few proteins that can improve function and proliferation and prolong the survival of beta-cells. Placental lactogen 1 is an attractive target for future therapeutic strategies in diabetes.

Animals↗
PubMed1982

Isolation, purification, and characterization of mouse placental lactogen.

Mouse placental lactogen was purified 1840-fold from BALB/c placentae from days 14-18 of gestation with an overall yield of 29%. The purification procedure included alkaline homogenization and extraction, ammonium sulfate precipitation, hydrophobic interaction chromatography on Phenyl-Sepharose, ion-exchange chromatography on CM- and DEAE-cellulose, and gel exclusion chromatography on Sephadex G-100. On 10% alkaline polyacrylamide gels, mouse placental lactogen had an Rf of 0.19. Electrophoresis in gels containing NaDodSO4 showed a single band with a mobility corresponding to a Mr of 23,000 +/- 1000. The isoelectric point, determined by isoelectric focusing in 8 M urea/5% 2-mercaptoethanol, was 7.1. When tested in the pigeon crop sac assay, 10 micrograms of mouse placental lactogen produced stimulation comparable with that evoked by 10 micrograms of ovine prolactin. In the rabbit mammary gland radioreceptor assay, mouse placental lactogen was 150% more potent than ovine prolactin in displacing 125I-labeled ovine prolactin from rabbit mammary gland membranes. Iodinated purified mouse placental lactogen could be displaced from rabbit mammary gland membranes by mouse placental lactogen, mouse prolactin, and ovine prolactin. Ovine prolactin was 45% as avid as mouse placental lactogen is displacing 125I-labeled mouse placental lactogen from rabbit mammary gland membranes. Mouse placental lactogen did not crossreact with antisera to mouse prolactin or mouse growth hormone in a radioimmunoassay.

Animals↗
PubMed1992

Epidermal growth factor stimulates mouse placental lactogen I but inhibits mouse placental lactogen II secretion in vitro.

This study was undertaken to determine whether epidermal growth factor (EGF) regulates the secretion of mouse placental lactogen (mPL)-I and mPL-II. Primary cell cultures were prepared from placentas from days 7, 9, and 11 of pregnancy and cultured for up to 5 days. Addition of EGF (20 ng/ml) to the medium resulted in significant stimulation of mPL-I secretion by the second day of culture in cells from days 7 and 9 of pregnancy and significant inhibition of mPL-II secretion by the third or fourth day of culture in cells from days 7, 9, and 11. Dose-response studies carried out with cells from day 7 of pregnancy demonstrated that the minimum concentration of EGF that stimulated mPL-I secretion and inhibited mPL-II secretion was 1.0 ng/ml. EGF did not affect the DNA content of the cells or cell viability, assessed by trypan blue exclusion, nor did it have a general effect on protein synthesis. There are three types of PL-containing giant cells in mouse placental cell cultures: cells that contain either mPL-I or mPL-II and cells that contain both hormones. Immunocytochemical analysis and the reverse hemolytic plaque assay indicated that EGF treatment was accompanied by a significant increase in the number of cells that produce mPL-I, but among the PL cells that contained mPL-I, there was no change in the fraction of cells that contained only mPL-I or the fraction that contained both mPL-I and mPL-II. In contrast, EGF treatment did affect the distribution of mPL-II among PL cells. In control cultures, about 75% of the cells that contained mPL-II also contained mPL-I, but in EGF-treated cultures, all of the cells that contained mPL-II also contained mPL-I. These data suggest that EGF regulates mPL-I and mPL-II secretion at least partly by regulating PL cell differentiation.

Animals↗
PubMed1993

Interleukin 6 inhibits mouse placental lactogen II but not mouse placental lactogen I secretion in vitro.

The mouse placenta produces several polypeptides belonging to the prolactin-growth hormone gene family, including mouse placental lactogen (mPL) I and mPL-II. The present study was undertaken to determine whether the secretion of mPL-I and mPL-II is regulated by interleukin 6 (IL-6), which is present in the placenta and has previously been reported to stimulate the secretion of pituitary members of this gene family. Effects of human and mouse IL-6 on mPL-I and mPL-II secretion were examined in primary cultures of placental cells from days 7, 9, and 12 of pregnancy. IL-6 caused a dose-dependent reduction in the mPL-II concentration in the medium of cells from days 9 and 12 of pregnancy but did not affect the mPL-II concentration in the medium of cells from day 7 of pregnancy or the mPL-I concentration in the medium of cells from days 7 or 9 of pregnancy. The lowest concentration of human IL-6 that significantly inhibited mPL-II secretion was 250 pM. The effect of IL-6 on the mPL-II concentration in the medium was due primarily to inhibition of mPL-II synthesis, which resulted at least partly from a decrease in the steady-state level of mPL-II mRNA. These data raise the possibility that IL-6 may regulate mPL-II production after midpregnancy in vivo.

Animals↗
PubMed1990

Transplantable rat choriocarcinoma cells express placental lactogen: identification of placental lactogen-I immunoreactive protein and messenger ribonucleic acid.

The purpose of this investigation was to evaluate the abilities of a transplantable rat choriocarcinoma (Rcho) to produce placental PRLs. The Rcho tumor was analyzed biochemically and histologically for the expression of placental PRLs. Expression of placental PRL mRNAs was determined by Northern blot and in situ hybridization analyses. Expression of placental PRL proteins was determined by Western blot and immunocytochemical analyses. Histologically, Rcho tumors were characterized by the appearance of giant cell surrounding hemorrhagic regions. Female rats bearing the Rcho tumor beneath their kidney capsule showed extensive mammary gland development. The Rcho tumors expressed placental lactogen-I (PL-I) mRNA and protein, but there was no evidence of placental lactogen-II (PL-II), PRL-like protein-A (PLP-A), or PRL-like protein-B (PLP-B). Rcho PL-I mRNA and proteins migrated as a 1-kilobase species and a 36- to 40-kDa species similar to those expressed by normal rat trophoblast tissues. The cell type responsible for Rcho PL-I production was the giant cell, similar to that observed in normal rat trophoblast tissues. In summary, we have demonstrated the production of PL-I by a transplantable rat choriocarcinoma (Rcho). The Rcho tumor resembles rat trophoblast tissue at early postimplantation stages (days 6-10 of gestation) and may be a useful tool for studying placental PRL expression during trophoblast differentiation.

Animals↗
PubMed1976

The purification and characterization of rabbit placental lactogen.

Rabbit placental lactogen, a polypeptide hormone functionally related to the growth hormone/prolactin family, was isolated from placenta by (NH4)2SO4 precipitation, gel filtration and ion-exchange chromatography on DEAE-and CM-cellulose. The hormone was purified to more than 90% homogeneity, as determined by end-group analysis. On disc gel electrophoresis at pH9.0 it migrates as a pair of closely spaced bands with mobilities of 0.489 (minor band) and 0.511 (major band), and its isoelectric point is 6.1. Its mol.wt. is 20600, as determined by sedimentation--equilibrium centrifugation, and 24200, as estimated by gel electrophoresis in sodium dodecyl sulphate. Its amino acid composition resembles that of rabbit growth hormone and rat prolactin, except for a lower glutamic acid and leucine content. Like the prolactins, rabbit placental lactogen has two tryptophan and six cysteine residues, and its N-terminus, valine, is identical with that for human placental lactogen. By radioimmunoassay, it does not cross-react with antisera to either rat growth hormone or rat prolactin; in addition, it does not cross-react with antisera to bovine placental lactogen by double immunodiffusion. The similarity of the biochemical characteristics of rabbit placental lactogen to the other non-primate placental lactogens lends further support to the hypothesis that these molecules occupy a more central position in the growth hormone/prolactin "tree" than do their primate counterparts.

Amino Acids↗
PubMed1986

Lactogenic effect of bovine placental lactogen on pregnant rabbit but not pregnant heifer mammary gland explants.

The biological function of bovine placental lactogen is unknown. However, bovine placental lactogen is known to bind prolactin receptors in rabbit mammary gland. This hormone was therefore cultured with rabbit mammary gland explants to confirm that it is lactogenic in this species. Mammary explants from pregnant heifers were also cultured with bovine placental lactogen to determine if the same preparation of hormone possessed similar lactogenic potential in homologous species. Bovine placental lactogen was tested over a range of concentrations from 10 to 500 ng/ml and was about 50 to 80% as potent as bovine prolactin when cultured with mammary explants from 19-d pregnant virgin rabbits. Lactogenic response was assessed by both the incorporation of [14C]acetate into lipid and by the synthesis of casein. Bovine placental lactogen displayed negligible lactogenic activity when cultured with mammary explants from 6 to 7-mo pregnant heifers. Lactogenic response was assessed using the same criteria as used with the rabbit mammary explants; in addition, accumulation of alpha-lactalbumin in the explants was also measured. Although bovine placental lactogen was lactogenic in the rabbit, the same hormone preparation was apparently not lactogenic in cattle. It is therefore vital to test for the biological activity of a hormone in a homologous system, because inappropriate conclusions may be drawn from the response obtained in a heterologous system.

Animals↗