Identification of the insulin-like growth factor binding proteins 5 and 6 (IGFBP-5 and 6) in human breast cancer cells.

Four estrogen receptor-positive (ER+) [MCF-7, T47D, ZR75 and BT474] and 3 ER- [Hs578T, MDA-MB-468 and MDA-MB-231] human breast cancer cell lines were examined for expression of the IGFBP-5 and IGFBP-6 genes. Northern blot analysis revealed that all cell lines, except MDA-MB-231, expressed IGFBP-5 mRNA. IGFBP-6 mRNA, however, was expressed only by the ER- cell lines.

Expression of the genes encoding the insulin-like growth factors and their receptors in the human ovary.

Insulin-like growth factor-I (IGF-I) and IGF-II have been proposed as potential regulators of ovarian function. To gain further insight as to the possible role(s) of the IGFs in human ovarian physiology, we have characterized the expression of the genes encoding the IGFs and their corresponding receptors in the human ovary using solution hybridization/RNase protection assays. IGF-I gene expression was evident in liver, placenta, and whole premenopausal ovary, but not in luteinized granulosa cells.

How distinct are the insulin and insulin-like growth factor I signalling systems?

Insulin and insulin-like growth factor I (IGF-I) are closely related peptides. Insulin is primarily involved in regulating carbohydrate, fat and protein metabolism. IGF-I, however, regulates growth and development of the whole organism as well as differentiated functions in specific tissues.

Cellular pattern of type-I insulin-like growth factor receptor gene expression during maturation of the rat brain: comparison with insulin-like growth factors I and II.

Insulin-like growth factors have a number of potent trophic effects on cultured neural tissue and most if not all of these effects appear to be mediated by the type-I insulin-like growth factor receptor. In order to establish the identity of cell types expressing this receptor in the rat central nervous system during development and maturity, we have used in situ hybridization to map sites of type-I insulin-like growth factor receptor mRNA synthesis in the developing and adult rat brain. In order to identify possible local sources of peptide ligands for this receptor, we have also mapped the sites of insulin-like growth factors I and II mRNA synthesis in parallel brain sections.

Altered expression of insulin-like growth factor-I (IGF-I) and IGF receptor genes after unilateral nephrectomy in immature rats.

There is a developmental difference in the initial phase of compensatory renal growth (CRG) following unilateral nephrectomy (UNX), in that CRG is GH-dependent in adult rats and GH-independent in immature rats. Furthermore, CRG in immature rats is associated with an increase in renal IGF-I mRNA, an effect not seen in adult rats. In this study we have examined the age-related differences in expression of the insulin-like growth factor-I (IGF-I) and IGF-II genes as well as in IGF-I and IGF-II receptors and membrane binding after UNX.

Evolutionary origins of intercellular communication systems: implications for mammalian biology.

Traditionally, the two major systems of intercellular communication (i.e. the nervous and endocrine systems) were considered separate functional and anatomical entities.

Insulin-like growth factor receptor gene expression in the rat ovary: divergent regulation of distinct receptor species.

The intraovarian insulin-like growth factor (IGF) system constitutes a triad composed of ligands, receptors, and binding proteins. Although conventional radioligand receptor assays have documented the presence of specific receptors for insulin and insulin-like peptides in some rat somatic ovarian cell types, the exact cellular localization and hormonal regulation of the receptors in question remain matters of inquiry. To reevaluate the very presence, cellular localization, and hormonal regulation of the IGF receptor gene family in the rat ovary, solution hybridization/RNase protection assays were used wherein ovarian total RNA (20 micrograms) from immature (21-23 days old) rats was hybridized with 32P-labeled type I IGF receptor, type II IGF/mannose-6-phosphate receptor, and insulin receptor riboprobes.

Expression, action, and steroidal regulation of insulin-like growth factor-I (IGF-I) and IGF-I receptor in the rat corpus luteum: their differential role in the two cell populations forming the corpus luteum.

The overall aim of this investigation was to examine the expression and steroidal regulation of insulin-like growth factor-I (IGF-I) and the IGF-I receptor in the rat corpus luteum and to examine the specificity of IGF-I action in the two luteal cell populations. We first examined whether the corpus luteum expresses the IGF-I and IGF-I receptor genes. Using a solution hybridization/RNase protection assay, IGF-I and IGF-I receptor mRNAs were represented by protected bands 224 and 265 bases in length, respectively.

Regulation of start site usage in the leader exons of the rat insulin-like growth factor-I gene by development, fasting, and diabetes.

Rat insulin-like growth factor-I (IGF-I) mRNAs with different 5'-untranslated region/prepeptide coding sequences result from transcription initiation in one of two leader exons. While not altering the mature IGF-I coding sequence, these different leaders potentially encode two distinct IGF-I prepeptides, one of 48 amino acids (exon 1) and one of 32 amino acids (exon 2). Within exon 1, transcription initiation is dispersed (i.

Evidence for an insulin-like growth factor autocrine-paracrine system in the retinal photoreceptor-pigment epithelial cell complex.

The interphotoreceptor matrix (IPM), lying between retinal photoreceptor and pigment epithelial (RPE) cells, contains insulin-like growth factor I (IGF-I) immunoreactivity that co-elutes with authentic human IGF-I in HPLC analyses. Cultured human RPE cells synthesize and release IGF-I, raising the possibility that the RPE serves as a source of IPM IGF-I in vivo. Photoreceptor rod outer segments and cultured monkey RPE cells express specific IGF-I receptors with alpha-subunits of 120 and 138 kDa, respectively.

Insulin-like growth factors: the ovarian connection.

A large body of information now supports the existence of a complete intraovarian insulin-like growth factor (IGF) system replete with ligands, receptors, and binding proteins. Although much remains to be learned, the emerging consensus would suggest that the intraovarian IGF system is concerned largely with the amplification of gonadotrophin hormonal action for the facilitation of follicular growth and development. Future studies are likely to address the central issue of indispensability and the documentation of a meaningful in vivo role for this and related putative intraovarian regulators.

Comparison of the counterregulatory hormone response to semisynthetic human insulin and purified porcine insulin in normal subjects and patients with type I diabetes mellitus.

The counterregulatory hormone responses to semisynthetic human insulin and purified porcine insulin were compared in 20 healthy volunteers (ten men and ten women) and 16 patients (8 men and 8 women) with type I diabetes mellitus (IDDM). In both groups blood glucose fell to similar levels following insulin administration; no difference in counterregulatory hormone response or hypoglycemic awareness was noted when comparing human to porcine insulin. However, when men were compared to women, significant differences were noted in basal glucagon, cortisol, and growth hormone levels, as well as in norepinephrine, prolactin, and cortisol responses to hypoglycemia.

Analysis of the human type I insulin-like growth factor receptor promoter region.

We isolated genomic fragments containing the 5' region of the human type I insulin-like growth factor receptor gene. A unique transcription start site was identified, defining a 1038 bp 5'-untranslated region. No TATA or CCAAT elements were identified in the proximal 480 nucleotides of 5'-flanking region.

Identification of multiple transcription start sites in the human insulin-like growth factor-I gene.

We have localized four transcription initiation sites in the human insulin-like growth factor-I (IGF-I) gene. Two transcription start sites were identified which result in a longer and shorter version of the leader derived from the known exon 1 of the IGF-I gene. Transcription starting at the upstream transcription initiation site results in a leader exon 1 of about 1155 nucleotides (nt), whereas transcription starting at the downstream initiation site results in a leader of about 240 nt.

Developmental regulation of insulin-like growth factor-I-stimulated glucose transporter in rat brain astrocytes.

Astrocytic glial cells from 1- and 21-day-old rat brains were established in primary culture to study the expression of insulin-like growth factor-I (IGF-I) receptors and IGF-I-stimulated glucose transporter (Glut-1). Astrocytes from both age groups expressed specific high affinity IGF-I receptors, whose relative affinities for IGF-I, IGF-II, and insulin were comparable. However, the total number of binding sites and IGF-I receptor mRNA levels were 148% and 240% higher in astrocytes from 21-day-old compared with 1-day-old brains.

Insulin-like growth factor I (IGF-I) receptors and IGF-I action in oligodendrocytes from rat brains.

Oligodendrocyte progenitor cells were prepared by mechanical dissociation of 1-day-old rat brain cultures. These cells undergo proliferation and differentiation into oligodendrocytes as demonstrated by the expression of proliferation and differentiation-related specific antigens. We have used this unique culture system to characterize insulin-like growth factor I (IGF-I) receptors and their action in the central nervous system (CNS).

Renal IGF-1 mRNA levels are enhanced following unilateral nephrectomy in immature but not adult rats.

The increase in IGF-1 gene expression following unilateral nephrectomy (UNX) in adult rats is controversial. In this study we have examined whether developmental differences exist in the effect of UNX on IGF-1 gene expression. Immature (23 days) and adult (4 months) Wistar rats underwent a sham operation or left UNX, and were sacrificed 24 or 48 hrs later.

Transcription initiation in the two leader exons of the rat IGF-I gene occurs from disperse versus localized sites.

Rat IGF-I mRNAs contain two different 5'-UTR sequences as a result of alternate splicing of leader exons. Using a combination of solution hybridization/RNase protection and primer extension assays, we have mapped the transcriptional start sites in these leader exons. There appear to be three putative transcription start sites in exon 1 spread over a 140-bp region, the most upstream of which defines a 381 bp-long exon 1.

Differential association of insulin-like growth factor I mRNA variants with polysomes in vivo.

Expression of the rat insulin-like growth factor I (IGF-I) gene results in a number of mature mRNA species that differ in size primarily at the 3' end due to differential polyadenylation site usage. Additionally, alternate splicing in both 5' and 3' regions produces RNAs which have the capacity to encode different IGF-I precursor peptides. We have analyzed total and polysomal RNAs using Northern blot analyses and solution hybridization/RNase protection assays to assess the in vivo translatability of these various IGF-I mRNA species.

Insulin-like growth factor I mRNA levels are developmentally regulated in specific regions of the rat brain.

The expression of mRNAs encoding insulin-like growth factor I (IGF-I) and the IGF-I receptor in the developing rat brain from embryonic day 16 to postnatal day 82 was analyzed using solution hybridization-RNase protection assays. Four distinct developmental patterns in the steady-state levels of IGF-I mRNA were seen. Specifically, the olfactory bulb showed a high perinatal level of IGF-I mRNA which declined dramatically by postnatal day 8.

Hormonal regulation of rat hypothalamic neuropeptide mRNAs: effect of hypophysectomy and hormone replacement on growth-hormone-releasing factor, somatostatin and the insulin-like growth factors.

Hormonal feedback regulation of hypothalamic peptides putatively involved in growth hormone (GH) regulation has been studied by measurement of steady-state mRNA levels in male hypophysectomized rats with or without thyroid hormone, corticosterone, testosterone or GH replacement. Hypothalamic GH-releasing factor (GRF) mRNA levels increased progressively following hypophysectomy to 420% of sham levels after 15 days while hypothalamic insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF-II) mRNA levels decreased to less than 40% of sham levels. Whole hypothalamic somatostatin mRNA levels were not significantly different from sham.

Retinoid modulation of insulin-like growth factor-binding proteins and inhibition of breast carcinoma proliferation.

Retinoids induce cellular differentiation and inhibit cellular proliferation. Proliferation of human breast carcinoma cells in vitro is markedly inhibited by these compounds. On the other hand, insulin-like growth factors (IGFs) and their receptors seem to be involved in the growth of certain breast carcinoma cells by autocrine or paracrine effects.