Biomedical subjects

F Talamantes

Publications and source records attributed to F Talamantes.

At least 109 records · Page 6Linked to original sources

PubMed1988

Trophoblastic giant cells of the mouse placenta as the site of proliferin synthesis.

Proliferin (PLF) is a PRL-related glycoprotein secreted by a number of mouse cell lines and by minced mouse placenta. To further investigate the hormone-like characteristics of PLF, we have determined the site of PLF synthesis and storage in the placenta and its concentration in blood serum during pregnancy. By immunohistochemical staining and in situ hybridization PLF protein and messenger RNA (mRNA) were localized to the trophoblastic giant cells. Individual cells contained both PLF and placental lactogen II. Trophoblastic giant cells appear to secrete PLF into the circulation since PLF was found at levels up to 5 micrograms/ml in the serum of pregnant mice by RIA and at somewhat lower concentrations in the amniotic fluid. Moreover, the serum concentration of PLF during pregnancy varied directly with the level of PLF mRNA in the placenta and with the number of placentas per animal. These findings are consistent with the hypothesis that PLF is a placental hormone; its function is not known.

Animals↗

PubMed1988

Pituitary factors regulating mouse placental lactogen-II secretion during the last half of pregnancy in mice.

Hypophysectomy of mice during the last half of pregnancy results in an increase in the maternal serum mouse placental lactogen-II (mPL-II) concentration. The present study was undertaken to isolate and identify the pituitary factors that regulate mPL-II. Administration of pituitary extracts from virgin and day 12 pregnant mice (five pituitaries per mouse, every 8 h, sc) and bilateral pituitary implants under the kidney capsule significantly inhibited the increase in the mPL-II concentration that occurs within 24 h after hypophysectomy on day 12 of pregnancy, which indicated that the pituitary secretes factors that regulate mPL-II. To characterize these factors biochemically, pituitaries from virgin female mice were incubated for 14 days, and the culture medium was pooled, concentrated, and then fractionated by gel exclusion chromatography on Sephadex G-100, followed by ion exchange chromatography on DEAE. The fraction from DEAE chromatography that contained predominantly mouse (m) GH as well as a very small amount of a substance with an approximate mol wt of 23K suppressed the posthypophysectomy rise in serum mPL-II. To determine whether purified PRL, GH, and the unknown 23K substance present in the active fraction from the DEAE column could suppress the posthypophysectomy rise in serum mPL-II, repeated injections and constant infusion of these substances were carried out in hypophysectomized mice. Repeated injections of purified mPRL and bovine (b) PRL and constant infusion of mPRL were without effect. Repeated injection of mGH at doses of 1 and 10 micrograms/mouse or of bGH at doses of 50, 150, and 450 micrograms/mouse were also not effective, but bGH injections at a dose of 5 mg/mouse suppressed the posthypophysectomy rise in serum mPL-II. Subsequently, two pools of mGH were prepared by ion exchange HPLC; mGH-A contained predominantly mGH as well as a very small amount of an unidentified 23K mol wt substance, and mGH-B contained only mGH. When mGH-A and mGH-B were infused at a constant rate into hypophysectomized pregnant mice, both suppressed serum mPL-II concentrations; there was no difference in activity between mGH-A and mGH-B. These results indicate that mGH, but not mPRL, regulates the serum PL-II concentration in the mouse. mPL-II secretion is under the inhibitory control of mGH, the concentration of which increases rapidly at the beginning of the last half of pregnancy.

Animals↗

PubMed1988

Gestational profile and affinity cross-linking of the mouse serum growth hormone-binding protein.

The modulation of the serum concentration of mouse GH-binding protein during gestation was characterized. A rapid increase in the concentration of the binding protein began on day 9 of pregnancy and peaked by day 15. The increase in the serum GH-binding protein concentration was preceded several days by an increase in the hepatic GH receptor concentration. The serum GH-binding protein was recognized by antibodies produced against the hepatic GH receptor, and its mol wt (major form mol wt, approximately 41,800) was similar to that of low mol wt forms of the hepatic GH receptor, demonstrating the similarity of the serum GH-binding protein and the hepatic GH receptor. The apparent affinity of the serum GH-binding protein for mGH in untreated serum samples from 17-day pregnant mice was 6.9 X 10(7) M-1. However, when the serum was treated to remove endogenous GH, the apparent affinity increased to 1.5 X 10(8) M-1. Likewise, the binding capacity of the GH-binding protein in serum differed in treated (60.1 nM) and untreated serum (101.2 nM).

Animals↗

PubMed1988

Biological, immunological, and binding properties of recombinant mouse placental lactogen-I.

Mouse placental lactogen-I (mPL-I) cDNA was inserted into a eukaryotic expression vector and introduced into Chinese hamster ovary cells. Cell lines that secrete high concentrations of mPL-I were isolated, and this glycoprotein was purified from the cell culture-conditioned medium. Recombinant mPL-I (mPL-Ir) is very similar to placental mPL-I (mPL-Ip) in its recognition by polyclonal antisera raised against either mPL-Ip or mPL-Ir, in displacing [125I]iodo-mPL-II from binding sites on mouse liver microsomal membranes, and in stimulating the synthesis of alpha-lactalbumin in primary cultures of mouse mammary epithelial cells. Structural comparison of mPL-Ir and mPL-Ip by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that mPL-Ir comprises several proteins with mol wt ranging from 34.5-38K, while mPL-Ip consists of a similar set of proteins with mol wt ranging from 36.5-42K. Treatment of the two proteins with neuraminidase resulted in similar 2-4K decreases in mol wt. Treatment of mPL-Ip with peptide:N-glycosidase-F to remove asparagine-linked oligosaccharide chains resulted in the formation of 28K and 29K mol wt species, while treatment of mPL-Ir with the same enzyme yielded 28K and 28.5K mol wt products.

Animals↗

PubMed1988

Isolation of two molecular weight variants of the mouse growth hormone receptor.

GH receptors (GHRs) have been shown by affinity cross-linking to be present in late pregnant mouse liver microsomes in three forms with cross-linked mol wts of 125,000, 62,000, and 56,000. The two lower mol wt forms of the receptor were partially purified by bovine GH-affinity chromatography of 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate-solubilized extracts of late pregnant mouse hepatic microsomes. The GHRs were identified from the partially purified receptor preparation and isolated by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isolated GHRs had mol wts of 40,700 and 37,500, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Enzymatic cleavage of N-linked glycosylation from the isolated GHRs reduced their apparent mol wts to 33,600 and 30,900, respectively. Sixteen of the amino-terminal 17 amino acid residues of the two isolated receptors were sequenced and determined to be identical. One amino acid residue in each of the proteins, at position 14, could not be identified. Rabbit polyclonal antiserum was produced against the isolated GHRs. The resulting antiserum precipitated the isolated 40,700 and 37,500 mol wt proteins as well as cross-linked mouse GHRs (including the high mol wt form of the receptor). However, the antiserum did not inhibit the binding of mouse GH to either membrane bound or 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate-solubilized GHRs.

Animals↗

PubMed1987

Identification and characterization of a heterogeneous population of growth hormone receptors in mouse hepatic membranes.

Covalent cross-linking of radiolabeled mouse growth hormone (125I-mGH) with the homobifunctional cross-linking agent bis(sulfosuccinimidyl)suberate (BS3) to microsomal membranes prepared from late pregnant mouse liver resulted in the labeling of three specific mGH binding proteins (receptors) with apparent Mr = 125,000, 62,000, and 56,000, as measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. These same three specifically labeled proteins were present, but with slightly lower apparent molecular weights, when samples were electrophoresed in the absence of reductant. Cross-linking of 125I-mGH to plasma membrane-enriched fractions of late pregnant mouse liver resulted only in the specific labeling of the two lower molecular weight receptors. Removal of all N-linked carbohydrate with peptide: N-glycosidase F resulted in decreasing the apparent molecular weights of the three receptor forms to 110,000, 50,000, and 46,000 for the 125,000, 62,000, and 56,000 molecular weight forms of the receptor, respectively. Smaller decreases in the molecular weights of all three receptor forms were also apparent after treatment with neuraminidase. However, the differences seen in the intact forms of the growth hormone receptor were also present in the deglycosylated receptors. The relationship between the three forms of the growth hormone receptor was further investigated by comparing the fragments produced by proteolytic digestion of the cross-linked receptors with Staphylococcus aureus protease and endoproteinase Lys-C. The fragments produced from all three receptor forms had very similar molecular weights, although there were slight molecular weight differences in the fragments produced by endoproteinase Lys-C digestion. The overall similarity of the fragments produced by the proteolytic digestions suggests that the three forms of the receptor are related.

Animals↗

PubMed1987

Immunological studies of rodent placental lactogens.

Structural relationships among the placental lactogens (PLs) from the mouse, the rat, and the hamster were examined by evaluating the cross-reactions between the PLs with a polyclonal antiserum to each PL. Two techniques, competitive radioimmunoassay displacement curves and immunoblotting of SDS-polyacrylamide gels, were used to evaluate the cross-reactions. By the first technique, a greater general similarity is found between mouse PL and rat PL than between either of these hormones and hamster PL. In contrast, the immunoblotting technique shows a greater similarity between mouse PL and hamster PL than between either of these hormones and rat PL. In the radioimmunoassays, the antibodies are reacting with the three-dimensional surfaces of the native PLs, while in the immunoblots the PLs have been denatured and unfolded. Thus, the different cross-reactions found by the two methods may reflect a dichotomy between the relationships in the primary and tertiary structures of the rodent PLs. Incomplete displacement by rat PL in the mouse PL radioimmunoassay suggests that mouse PL and hamster PL appear to share at least one surface feature that is completely absent on rat PL. All three anti-PL antisera react with multiple molecular weight bands in preparations of mouse PL and rat PL (but not hamster PL), indicating that mouse PL and rat PL are composed of several different molecular weight species while hamster PL consists of a single molecular weight form.

Animals↗

PubMed1987

Purification and partial characterization of prolactin from the California ground squirrel (Spermophilus beecheyi).

Prolactin (Prl) secreted by cultured ground squirrel (Spermophilus beecheyi) pituitaries (SbPrl) was purified by gel filtration on Sephadex G-100 and ion-exchange chromatography on Polybuffer Exchanger 94. Purification from culture medium from 190 pituitaries yielded 1.1 mg of purified SbPrl. The SbPrl has an apparent molecular weight of 27,000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, an isoelectric point of 6.3, and does not contain any asparagine-linked carbohydrate. Purified SbPrl displaces 125I-labeled ovine Prl from binding sites on lactating rabbit mammary gland membranes and stimulates secretion of alpha-lactalbumin by cultured mouse mammary gland epithelial cells.

Animals↗

PubMed1987

Development of an homologous radioimmunoassay for secreted prolactin from the California ground squirrel (Spermophilus beecheyi).

A sensitive homologous radioimmunoassay was developed for secreted prolactin from the California ground squirrel (Spermophilus beecheyi). S. beecheyi plasma and pituitary extracts displaced 125I-labeled S. beecheyi prolactin in a parallel manner with S. beecheyi prolactin (sbPRL). Mean minimum sensitivity of the assay was 0.21 ng/ml, and mean intra- and interassay coefficients of variation were 4.1% and 14.5%, respectively. The assay was used to measure basal prolactin concentrations in male and female ground squirrels at various stages of their annual reproductive cycles. Mean concentrations in nonpregnant, nonlactating young females, pregnant females, and lactating females were 1.63, 11.35, and 10.86 ng/ml, respectively. Mean concentrations in nonreproductive and breeding males were 1.50 and 9.81 ng/ml, respectively. Finally, the assay was used to evaluate cross-reactivity between sbPRL and prolactins and growth hormones from other rodent species. Of the tested hormones, only hamster prolactin showed any cross-reactivity with sbPRL (about 0.03%).

Animals↗

PubMed1987

Effects of fasting on serum lactogenic hormone concentrations during mid- and late pregnancy in mice.

Hormonal and metabolic responses to fasting were studied in pregnant Swiss Webster mice. Food was removed from pregnant mice 12, 24, 36, or 48 h before death on day 12 or 15 of pregnancy. Serum mouse placental lactogen-II (mPL-II), mouse growth hormone (mGH), mouse prolactin (mPRL), free fatty acids (FFA), and glucose concentrations were determined for each group. In comparing fasted animals with fed controls, there was a significant increase in the serum mPL-II concentration after 24 and 48 h of fasting on day 12 and after 12, 36, and 48 h of fasting on day 15. Fasting significantly decreased the glucose and increased the FFA concentration of the serum at all fasting periods. Fasting had no effect on serum mPRL or mGH concentrations. In the second part of this study, pregnant mice were fasted for 24 h and then refed for an additional 24 h before being killed on day 12 of pregnancy. The changes in serum mPL-II, glucose, and FFA concentrations that occurred after a 24-h fast on day 12 of pregnancy were completely reversed by refeeding the animals for 24 h. Results from both studies indicate the involvement of mPL-II in the maternal response to fasting in pregnant mice.

Animals↗

PubMed1987

Purification and partial characterization of two prolactin-like glycoprotein hormone complexes from the midpregnant mouse conceptus.

Two PRL-like glycoprotein hormone complexes were purified from the medium of cultured mouse conceptuses from day 10 of pregnancy: mouse placental lactogen-I (mPL-I) (29-32K), and mPL-I (36.5-42K). Sodium dodecyl sulfate-gel electrophoresis revealed that mPL-I (36.5-42K) is a complex of five proteins with mol wt of 36.5K, 37.5K, 39K, 40.5K, and 42K. Deglycosylation with peptide: N-glycosidase F or trifluoromethanesulfonic acid produced a single 29K protein. mPL-I (36.5-42K) was also sensitive to neuraminidase, but not to endo-beta-N-acetylglucosaminidase H or bacterial alkaline phosphatase. The production of intermediates from partial digestion of mPL-I (36.5-42K) with endo-beta-N-acetylglucosaminidase F indicated the presence of multiple glycosylation sites. mPL-I (29-32K) is a complex of three proteins with mol wt of 29K, 30.5K, and 32K. Treatment with peptide:N-glycosidase F or trifluoromethanesulfonic acid reduced the mol wt of the 30.5K and 32K bands to 28K. The 30.5K band was sensitive to endo-beta-N-acetylglucosaminidase H and endo-beta-N-acetylglucosaminidase F, but the 32K band was not. Neither band was sensitive to neuraminidase or bacterial alkaline phosphatase. The 29K band was resistant to all chemical and enzymatic treatments and is probably not glycosylated or phosphorylated. In the nonreduced state, neither form of mPL-I showed an increase in mobility over that of its reduced counterpart on sodium dodecyl sulfate-gel electrophoresis, indicating that neither form of mPL-I contains the large disulfide loop common to hormones of the PRL family. After iodination, all component proteins of both forms of mPL-I were found to bind to day 17 pregnant mouse liver membranes and were displaceable by excess mPL-II. In a radioreceptor assay, 125I-labeled mPL-I (36.5-42K) was displaced by mPRL or mPL-II, but not by mGH. An antiserum to both forms of mPL-I was generated, and a RIA employing mPL-I (36.5-42K) as the standard and radioligand was developed. Dilutions of day 10 pregnant maternal mouse serum and placental homogenate and a partially purified fraction of mPL-I (29-32K) produced displacement curves parallel to that of mPL-I (36.5-42K) standard curve. Five micrograms of mPRL, mPL-II, or mGH or 10 microliter day 17 pregnant or male mouse serum did not displace the radioligand from the antibody. mPL-I (36.5-42K) was lactogenic, but it did not possess LH-like bioactivity.

Animals↗

PubMed1987

The lipolytic effects of mouse placental lactogen II, mouse prolactin, and mouse growth hormone on adipose tissue from virgin and pregnant mice.

The lipolytic activities of three structurally related mouse hormones, placental lactogen II (mPL-II), GH (mGH), and PRL (mPRL), and human PL (hPL) were investigated. Adipose tissue was obtained from virgin and day 12 and day 16 pregnant mice. Lipolytic activity was assessed by the ability of the hormones to stimulate glycerol release from fat explants in the presence of dexamethasone and by the ability of the hormones to sensitize adipose tissue to the lipolytic stimulus theophylline. In the first experiment, adipose tissue explants were incubated in Krebs-Ringer buffer with 0.0, 0.1, 0.5, 1.0, 5.0, and 10.0 micrograms/ml hormone for 4 h. mGH was lipolytic at a concentration of 0.5 micrograms/ml or greater in adipose tissue from both virgin and pregnant mice. mPRL was lipolytic at a concentration of 5.0 micrograms/ml or greater in adipose tissue from virgin mice. In adipose tissue from pregnant mice mPRL was not lipolytic in day 12 tissue, but it was lipolytic at a concentration of 5.0 micrograms/ml in day 16 tissue. mPL-II and hPL did not stimulate glycerol release in mouse adipose tissue from virgin or pregnant mice. In the second experiment preincubating adipose tissue from virgin mice in the presence of 0.5 or 5.0 micrograms/ml mGH significantly increased the ability of the tissue to respond to theophylline; however, mGH did not induce this response in adipose tissue from pregnant mice, mPRL, mPL-II, and hPL did not increase theophylline-induced lipolysis in adipose tissue from either virgin or pregnant mice. These results indicate that two lipolytic mechanisms are activated in adipose tissue from mice; mGH can activate both mechanisms, whereas mPRL can activate only one.

Adipose Tissue↗

PubMed1987

Hamster placental lactogens: gestational profiles and high molecular weight forms.

We previously reported the purification of a lactogenic protein, hamster placental lactogen (haPL; now designated haPL-II) from late pregnant hamster placentas. In this study the lactogenic factors in maternal serum during the second half of pregnancy were measured using RIAs for haPL-II and haPRL and a RRA for total lactogenic activity. haPL-II was first detectable on day 10 of pregnancy and reached a maximal concentration [12.3 +/- 0.8 microgram/ml (mean +/- SEM); n = 6] on day 16 (term). PRL concentrations were relatively low during the second half of gestation. Significant amounts of lactogenic activity that could not be ascribed to haPL-II or haPRL were detected throughout this period, with maximal concentrations on days 10-12. Gel filtration chromatography of day 10 serum gave an apparent mol wt of 35,000 for this lactogenic factor. A lactogenic factor with a similar mol wt (37,000) was detected in an extract of day 10 placenta. This lactogenic factor was designated haPL-I. The most prominent forms of haPL-II in day 16 serum were several disulfide-bonded forms with mol wt greater than 200,000. Smaller quantities of lower mol wt forms, including monomeric haPL-II, were present, but circulated as noncovalently bound complexes with mol wt greater than 100,000. Complete conversion to monomeric haPL-II was found only after treatment with both sodium dodecyl sulfate and 2-mercaptoethanol. The high mol wt forms of haPL-II in maternal serum were composed of two different monomeric species of haPL-II.

Animals↗

PubMed1987

Molecular cloning and expression of mouse placental lactogen I complementary deoxyribonucleic acid.

The mouse midpregnancy lactogen or placental lactogen I (mPL-I) is encoded by a 1.0-kilobase mRNA that appears transiently during gestation, with maximal amounts accumulating in the placenta at day 10 of pregnancy. Several cDNA clones for mPL-I have been isolated from a lambda gt11 expression library constructed from day 10-placental RNA. The cDNA sequence indicates that mPL-I is synthesized as a 224 amino acid precursor, and is secreted as a 194 amino acid glycosylated hormone. The deduced amino acid sequence of mPL-I is highly homologous to the known members of the PRL family in the mouse, and hybridization analysis indicates that the mouse genome contains several mPL-I genes. Introduction of the mPL-I cDNA in an expression vector into cultured mouse cells results in the synthesis and secretion of glycosylated mPL-I protein that is recognized by anti-mPL-I antiserum and is biologically active.

Amino Acid Sequence↗

PubMed1986

Molecular cloning of mouse placental lactogen cDNA.

We have isolated a cDNA clone for the 23-kDa mouse placental lactogen II (mPL-II) from a phage lambda gt11 expression library containing cDNA synthesized from BALB/c placental RNA. Translation in vitro of placental mRNA selected by hybridization to the mPL-II cDNA clones yields a 26-kDa polypeptide that is the size of the expected precursor protein and that is immunoprecipitated with anti-mPL-II antiserum. The mPL-II cDNA clones hybridize to a 1.0-kilobase placental-specific mRNA. This mRNA, found in the fetal portion of the placenta, appears as early as day 10 of gestation and increases to a maximal level by day 12. The mPL-II cDNA nucleotide sequence has been determined. This sequence contains an open reading frame encoding a polypeptide of 222 amino acids with the amino-terminal 31 amino acids forming the signal sequence for secretion. The predicted secreted protein has 51% amino acid homology with mouse prolactin.

Amino Acid Sequence↗

PubMed1986

Purification and partial characterization of hamster placental lactogen.

A radioreceptor assay for PRL-like activity was used to monitor the purification of a lactogenic protein, hamster placental lactogen (haPL), from late pregnant hamster placentae. Investigations of the PRL-like activity in placental extracts demonstrated that haPL is subject to disulfide-related aggregation phenomena that are not observed for mouse PL. By inclusion of 2-mercaptoethanol in the buffers used for purification, monomeric haPL was obtained. A 750-fold purification was achieved by ammonium sulfate precipitation and chromatography on phenyl-Sepharose, TSK diethylaminoethyl-650S, hydroxylapatite, and Sephadex G-100. This procedure yielded 6.2 mg (by dry wt) of purified haPL from 286 g 15-day pregnant hamster placentae, with an overall yield of 20%. The purified haPL has a mol wt of 25,200 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point of 8.8. haPL is lactogenic as judged by its ability to compete for lactogen binding sites on rabbit mammary gland membranes and to stimulate secretion of alpha-lactalbumin by cultured mouse mammary gland epithelial cells.

Animals↗

PubMed1986

The effect of hypophysectomy on serum placental lactogen and progesterone in the mouse.

Hypophysectomy of pregnant mice on days 10, 12, and 16 of gestation resulted in a large and rapid (12-24 h postoperatively) increase in serum placental lactogen (mPL) concentrations, as measured by homologous RIA. Serum progesterone (P4) concentrations decreased compared to those in intact and sham-operated controls. Significantly, the increase in serum mPL in mice hypophysectomized on days 10 and 12 preceded any decrease in serum P4 concentrations by at least 24 h, suggesting that two indirectly related mechanisms may be involved in the control of the serum concentrations of these hormones. The weight of the uterus, including the feto-placental units, placental weight, and placental content of mPL did not differ between intact, sham-operated, and hypophysectomized groups. The gestational profiles of serum GH and PRL concentrations were similar in the sham-operated and intact controls. Although serum P4 concentrations decreased after hypophysectomy on days 10 and 12 of gestation, the maintenance of the pregnancy was not affected; thus, the reduced concentrations of serum P4 (approximately 50% of control by day 16) were adequate to allow the pregnancy to continue. Hypophysectomy on day 16 of gestation resulted in spontaneous abortion 48 h postoperatively in all but one animal. We conclude that the absence of some pituitary factor(s) results in a rapid increase in serum mPL, while a concomitant, albeit gradual, decrease in serum P4 begins 48 h postoperatively. Therefore, when the pituitary no longer contributes to the luteotropic complex of the midpregnant mouse, an increase in serum mPL alone cannot maintain serum P4 concentrations at control values.

Animals↗

PubMed1986

Neonatal diethylstilbestrol treatment: response of prolactin to dopamine or estradiol in adult mice.

The effects of neonatal diethylstilbestrol (DES) treatment on pituitary PRL response to dopamine (DA) inhibition or estrogen stimulation were studied in C3H/MTV+ mice at 10 weeks, 5 months and 8 months of age using synthesis and release of [3H]PRL by the pituitary as endpoints. In the DA study, anterior pituitaries from ovariectomized or intact, neonatally hormone-treated mice were incubated for 6 h in the presence or absence of DA. In the estrogen study, serum and anterior pituitaries were obtained from ovariectomized neonatally hormone-treated mice injected with oil or 17 beta-estradiol for 7 days before death. Neonatal treatment of mice with 2.5 micrograms/day DES altered basal [3H]PRL synthesis and release as well as circulating PRL concentrations. The results of analysis of variance indicated a significant interaction between the effects of neonatal hormone treatment and DA treatment on [3H]PRL release. Neonatal DES treatment did not alter the response of pituitary PRL to estrogen treatment at the ages examined.

Animals↗