Expression of aminopeptidase B in the developing and adult rat retina.

Aminopeptidase B (Ap-B), a ubiquitous enzyme, catalyses the amino-terminal cleavage of basic residues of peptide or protein substrates, indicating a role in precursor processing. The physiological function of Ap-B still remains an open question, even though its activity suggests that it could be involved in inflammatory processes and proliferation of tumor cells. This study was conducted to determine the expression of Ap-B in the developing and adult retina as a path to envisage physiological roles of Ap-B.

Age-associated changes in hypothalamic and pituitary neuroendocrine gene expression in the rat.

A cDNA membrane array displaying 1183 probes was used to detect hypothalamic and pituitary changes in gene expression accompanying ageing and age-associated pituitary macroadenomas. Four groups of male Sprague-Dawley rats (3-, 15-, 24-month-old and 24-month-old with prolactinoma) were compared in two independent hybridizations. cDNA array data were confirmed and completed by comparative reverse transcriptase-polymerase chain reaction on selected genes.

Desensitization of type 1 angiotensin II receptor subtypes in the rat kidney.

Differences involving serine residues in the sequence of the carboxyl-terminal tail of type 1 angiotensin II (Ang II) receptor subtypes AT(1A) and AT(1B) suggest differences in desensitization ability. We examined the Ang II-induced homologous desensitization patterns of both receptor subtypes in freshly isolated renal structures: glomerulus (Glom), afferent arteriole, and cortical thick ascending limb (CTAL), whose content in each subtype mRNA is different, by measuring variations in intracellular calcium concentration. A preexposure to a maximal dose of Ang II, followed by a second application of the same concentration, induced: 1) a complete desensitization in Glom, where AT(1A) and AT(1B) mRNAs were expressed in similar proportions, and 2) no or partial desensitization in afferent arteriole and CTAL, where AT(1A) mRNA was predominant.

Differential pituitary gene expression profiles associated- to aging and spontaneous tumors as revealed by rat cDNA expression array.

Aging of the rat pituitary is often accompanied by the occurrence of adenomas. We asked whether complementary DNA hybridization array was adapted to identify gene expression patterns linked to aging and associated spontaneous adenomas. Thus, [32P]dATP-labeled cDNAs were prepared from pituitaries of three month-old rats (Y) and tumor-bearing 20-28-month-old rats (OT).

Effect of 17beta-estradiol on somatostatin receptor expression and inhibitory effects on growth hormone and prolactin release in rat pituitary cell cultures.

In the present study, we tested whether 17beta-estradiol (E2)-induced PRL sensitivity to somatostatin-14 (SRIF) involves selective up-regulation of discrete somatostatin receptor subtypes (ssts) in primary cultures of female rat pituitary cells. The efficacy of the endogenous peptide SRIF to inhibit GH and PRL secretion and cAMP accumulation was compared with those of octreotide (OCT), BIM-23052, BIM-23056, and BIM-23268, which have been reported to be relatively selective for rat sst2, sst3, and sst5. Experiments were performed in steroid-depleted media supplemented or not with 1 nM E2 for 96 h.

Hypothalamic and hypophyseal regulation of growth hormone secretion.

1. Regulation of pulsatile secretion of growth hormone (GH) relies on hypothalamic neuronal loops, major transmitters involved in their operation are growth hormone releasing hormone (GHRH) synthetized mostly in arcuate nucleus (ARC) neurons, and somatostatin (SRIH), synthetized both in hypothalamus periventricular (PVe) and ARC neurons. 2.

Multiple pituitary and ovarian defects in Krox-24 (NGFI-A, Egr-1)-targeted mice.

The zinc finger transcription factor Krox-24 (NGFI-A, Egr-1) is encoded by an immediate-early serum response gene expressed in various physiological situations and tissues. To investigate its function, we have created a null allele. Mice homozygous for the mutation have a reduced body size, and both males and females are sterile.

Site-specific methylation of the rat prolactin and growth hormone promoters correlates with gene expression.

The methylation patterns of the rat prolactin (rPRL) (positions -440 to -20) and growth hormone (rGH) (positions -360 to -110) promoters were analyzed by bisulfite genomic sequencing. Two normal tissues, the anterior pituitary and the liver, and three rat pituitary GH3 cell lines that differ considerably in their abilities to express both genes were tested. High levels of rPRL gene expression were correlated with hypomethylation of the CpG dinucleotides located at positions -277 and -97, near or within positive cis-acting regulatory elements.

CpG methylation represses the activity of the rat prolactin promoter in rat GH3 pituitary cell lines.

In the present report, we have investigated the role of DNA methylation on the binding and trans-acting properties of transcription factors involved in the regulation of the rat prolactin (rPRL) gene, specifically Pit-1. To this aim we took advantage of a model system composed of three GH3 rat pituitary tumor cell lines that greatly differed in the extent of rPRL gene methylation and in the level of rPRL gene expression. Northern blot analyses indicated that identical species of Pit-1 mRNA were present to similar extent in the three GH3 cell lines.

Multiple intracellular signallings are involved in thyrotropin-releasing hormone (TRH)-induced c-fos and jun B mRNA levels in clonal prolactin cells.

In mammosomatotropes GH3B6 cells, one of the primary responses to thyrotropin-releasing hormone (TRH) is the parallel induction of two proto-oncogenes, c-fos and jun B, which code for constituents of AP1 transcription factor. To better understand the mode of action of TRH and to look for possible functions of c-fos and jun B in these cells, we have investigated the role of different intracellular signals in the induction of each proto-oncogene on the one hand, and on prolactin (PRL) release and PRL gene expression on the other hand. Northern and dot-blot analyses revealed that the activation of protein kinase C (PKC)-, Ca(2+)- or adenylyl cyclase-dependent pathways acutely increased both c-fos and jun B transcripts.

[Stimulation of C-fos and jun B proto-oncogenes: potential role of TRH effects in clone cell line with prolactin (GH3B6)].

The hypothalamic neuropeptide TRH, which stimulates prolactin (PRL) release and PRL gene transcription, also raises c-fos proto-oncogene mRNA levels in GH3B6 rat pituitary cells. C-fos is assumed to be involved in the transduction of external signals to the nucleus as a component of AP1 transcription factor, a protein complex that contains a member of the jun proto-oncogene family. We have thus looked for the member(s) of the jun family that could be the partner of c-fos in TRH-stimulated GH3B6 cells.

Production and characterization of polyclonal anti-idiotypic anti-TRH antibodies: application to the study of pituitary TRH receptor.

cDNA encoding the thyrotropin-releasing hormone receptor (TRH-R) was recently cloned in rat pituitary prolactin cells and in mouse thyrotropes. The molecular weights of the protein sequences obtained are 46.6 and 44.

Thyrotropin-releasing hormone stimulates in parallel jun B and c-fos messenger ribonucleic acids in GH3B6 pituitary cells: comparison with PRL secretion.

The hypothalamic neuropeptide TRH stimulates PRL release and PRL gene transcription in GH3B6 rat pituitary cells. In this model, TRH also raises c-fos proto-oncogene mRNA levels. c-fos is assumed to be involved in the transduction of external signals to the nucleus as a component of AP1 transcription factor, a complex that contains a member of the jun proto-oncogene family.

Chronic growth hormone (GH) hypersecretion induces reciprocal and reversible changes in mRNA levels from hypothalamic GH-releasing hormone and somatostatin neurons in the rat.

Effects of growth hormone (GH) hypersecretion on somatostatin-(SRIH) and GH-releasing hormone (GHRH) were studied by in situ hybridization and receptor autoradiography in rats bearing a GH-secreting tumor. 6 and 18 wk after tumor induction, animals displayed a sharp increase in body weight and GH plasma levels; pituitary GH content was reduced by 47 and 55%, while that of prolactin and thyrotropin was unchanged. At 18 wk, hypothalamic GHRH and SRIH levels had fallen by 84 and 52%, respectively.

Properties of monoclonal antibodies to thyroliberin (TRH) induced by different immunogens: comparison with pituitary TRH receptor.

Thyroliberin E-H-P-NH2 (TRH) is a small neuropeptide pGlu-His-Pro-NH2 widely distributed in neural sites. The aim of this work was to obtain an antibody molecule with the nearest properties to that of TRH-receptor in GH3 cells. Different TRH-protein conjugates were prepared and utilized to induce monoclonal antibodies in mice.

Secretogranin I (chromogranin B) mRNA accumulation is hormonally regulated in GH3B6 rat pituitary tumor cells.

Secretogranin I (SgI; chromogranin B) belongs to a class of acidic tyrosine-sulfated secretory proteins believed to play a role in the secretory process of endocrine cells. Our aim here was to compare the levels of SgI mRNA to that of prolactin (PRL) and growth hormone (GH), using rat pituitary cell lines. As far as the constitutive expression is concerned, we found a positive correlation between SgI mRNA and PRL mRNA levels.

[Neuropeptides and regulation of various proto-oncogenes in cultured anterior pituitary cells].

The analysis of the characteristics of a number of proto-oncogenes reveals some similarities with the site of action (plasma membrane receptor, nucleus) or the mechanisms of action (coupling protein of the "G" family, transcriptional activity) of neuropeptides and namely hypophysiotropic hypothalamic neuropeptides. The example illustrated in this review concerns the induction of the early nuclear oncogene c. fos by TRH in a prolactin secreting rat pituitary cell line.

Thyroliberin and dihydropyridines modulate prolactin gene expression through interacting pathways in GH3 cells.

The stimulation of PRL gene transcription by TRH involves the two branches of the phosphatidyl inositol pathway as shown by pharmacological mobilization of intracellular Ca2+ stores and activation of protein kinase C. However, TRH receptor occupancy also results in the activation of voltage-dependent Ca2+ channels. Thus, we attempted to determine whether a specific class of voltage-dependent Ca2+ channels, the dihydropyridine (DHP)-sensitive Ca2+ channels, might also be involved in the transcriptional action of TRH.

[Hypothalamic hypophysiotropic neuropeptide receptors].

The present review is dealing with the five major hypothalamic hypophysiotropic neuropeptides (H.H.N.

Preferential role of calcium in the regulation of prolactin gene transcription by thyrotropin-releasing hormone in GH3 pituitary cells.

TRH induces two separate events in pituitary PRL cells. It increases the release of stored PRL and enhances the rate of PRL gene transcription, which results in an increased steady state concentration of PRL messenger RNA (mRNA) and a concomitant augmentation of PRL production. The mechanisms underlying the release process involve the activation of phosphatidylinositol turnover which generates inositol 1,4,5-trisphosphate and 1,2-diacylglycerol.