Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of the present study was to investigate the role of insulin-like growth factor I in the development of cardiac hypertrophy in two-kidney, one clip hypertension by relating growth hormone receptor and insulin-like growth factor I receptor mRNA levels to insulin-like growth factor I gene transcription using a solution hybridization/RNase protection assay. Two-kidney, one clip hypertension was induced in male Wistar rats, and experiments were performed 2, 4, 7, and 12 days after surgery. Systolic blood pressure was elevated 2, 7, and 12 days after clipping (P < .001). Left ventricular weights were increased 2, 4, 7, and 12 days after surgery (P < .01). Associated with the rise in blood pressure, left ventricular insulin-like growth factor I mRNA was increased 2, 7, and 12 days after surgery (P < .01). Furthermore, growth hormone receptor and insulin-like growth factor I receptor gene expression increased specifically in the left ventricle of renal hypertensive rats (P < .05 and P < .001, respectively). Left ventricular growth hormone receptor mRNA peaked 7 days after induction of renal artery stenosis. These results show that insulin-like growth factor I, growth hormone receptor, and insulin-like growth factor I receptor mRNA increase in the pressure-overloaded left ventricle of two-kidney, one clip rats, suggesting a role for insulin-like growth factor I and the growth hormone/insulin-like growth factor I axis in the development of cardiac hypertrophy.
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PMID:Cardiac insulin-like growth factor I and growth hormone receptor expression in renal hypertension. 861 16

There is increasing evidence that activation of the insulin-like growth factor I (IGF-I) receptor plays a major role in the control of cellular proliferation of many cell types. We studied the mitogenic effects of IGF-I, IGF-II, and epidermal growth factor (EGF) on growth-arrested HT-3 cells, a human cervical cancer cell line. All three growth factors promoted dose-dependent increases in cell proliferation. In untransformed cells, EGF usually requires stimulation by a "progression" factor such as IGF-I, IGF-II, or insulin (in supraphysiologic concentrations) in order to exert a mitogenic effect. Accordingly, we investigated whether an autocrine pathway involving IGF-I or IGF-II participated in the EGF-induced mitogenesis of HT-3 cells. With the RNase protection assay, IGF-I mRNA was not detected. However, IGF-II mRNA increased in a time-dependent manner following EGF stimulation. The EGF-induced mitogenesis was abrogated in a dose-dependent manner by IGF-binding protein 5 (IGFBP-5), which binds to IGF-II and neutralizes it. An antisense oligonucleotide to IGF-II also inhibited the proliferative response to EGF. In addition, prolonged, but not short-term, stimulation with EGF resulted in autophosphorylation of the IGF-I receptor, and coincubations with both EGF and IGFBP-5 attenuated this effect. These data demonstrate that autocrine secretion of IGF-II in HT-3 cervical cancer cells can participate in EGF-induced mitogenesis and suggest that autocrine signals involving the IGF-I receptor occur "downstream" of competence growth factor receptors such as the EGF receptor.
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PMID:Insulin-like growth factor II mediates epidermal growth factor-induced mitogenesis in cervical cancer cells. 861 25

Expression of genes encoding insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II) and type I insulin-like growth factor receptor (IGFr) was measured in theca and granulosa cells from the ovary of the laying hen, using an RNase protection assay. Expression of genes encoding IGF-I and -II was confined to theca tissue and expression was not detected in granulosa cells. In contrast, expression of genes encoding IGFr in granulosa cells was significantly greater than that in theca tissue. The 98 base IGF-II probe was similar to a region of the second coding exon of chicken IGF-II and produced multiple RNase-protected RNA hybrids. Theca RNA from follicles at all stages of development produced RNase-protected hybrids of size 98, 96 and 90 bases; however, an additional band (66 bases) was also observed in theca RNA from small yellow follicles. The stage of follicular development during which maximum amounts of the 66 base RNase-protected fragment was detected correlates with the stage at which small follicles are selected for recruitment into the follicular hierarchy. The results provide evidence for the involvement of IGFs in the intraovarian control of ovarian function in a non-mammalian species, and highlight the importance of IGF-II in this process.
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PMID:Insulin-like growth factor I (IGF-I), IGF-II and type-I IGF receptor gene expression in the ovary of the laying hen. 866 33

In several species, including humans, circulating insulin-like growth factor I (IGF-I) levels increase during the onset of puberty, suggesting that this peptide contributes to attaining sexual maturity. Because IGF-I elicits LHRH release from the median eminence (ME) of immature female rats in vitro, we hypothesized that it may represent one of the peripheral signals suspected to link somatic development to the LHRH-releasing system at puberty. We now present evidence in support of this concept. Quantitation of IGF-I messenger RNA (mRNA) levels by ribonuclease protection assay revealed that expression of the IGF-I gene did not change in the medial basal hypothalamus or preoptic area of female rats during peripubertal development. In contrast, the contents of both IGF-Ia and IGF-Ib mRNA, the two alternatively spliced forms of the IGF-I gene, increased significantly in the liver during the early proestrous phase of puberty. This change was followed by an elevation in serum IGF-I levels during the late proestrous phase of puberty along with a concomitant increase is serum gonadotropin levels. The proestrous change in serum IGF-I levels was accompanied by a selective increase in IGF-I receptor (IGF-IR) mRNA in the ME. Small doses of IGF-I (2-200 ng), administered intraventricularly, effectively induced LH release in both juvenile and peripubertal female rats, an increase prevented by prior immunoneutralization of LHRH actions. Importantly, intraventricular injections of IGF-I (20 ng), administered twice daily in the afternoon to immature animals, significantly advanced puberty. Thus, these results suggest that IGF-I of peripheral origin contributes to the initiation of female puberty by stimulating LHRH release from the hypothalamus, an effect that appears to be amplified by the increased synthesis of IGF-I receptors in the ME during first proestrus.
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PMID:Insulin-like growth factor I of peripheral origin acts centrally to accelerate the initiation of female puberty. 875 38

The rat insulin-like growth factor I (IGF-I) gene is characterized by the presence of multiple mRNA transcripts, which differ in the 5'- and/or 3'-untranslated regions (UTRs). Transcript initiation occurs in either exon 1 or exon 2, giving rise to mRNA species which differ in the length and sequence of the 5'-UTR, while further variation is due to multiple transcription start sites and differential splicing within exon 1. This heterogeneity is indicative of multifaceted regulation of gene expression, and it is likely that differences in the nature of transcript expression reflect cell-specific regulation. As IGF-I is an important factor in skeletal growth and development, the aim of this study was to determine the pattern of transcript expression in rat whole bone and osteoblast-enriched cultures isolated from long bones. The relative proportions of transcripts differing in the 5'-UTR were determined by RNase protection assays and compared to expression in rat liver. These studies revealed a significantly lower expression of exon 2-derived transcripts in bone cells compared to liver (approximately 10% compared to 40% of total transcripts). There were also important differences in start site usage in exon 1 in bone cells. In osteoblastic cells, transcripts initiated at start site 3 were the predominant species (50% +/- 12% of total exon 1-derived mRNAs; Mean +/- SD) whereas the alternately spliced transcripts represented only 20% +/- 3%. This was in contrast to the profile in liver in which 47% +/- 9% of total exon 1-derived transcripts were the alternately spliced mRNAs, but start site 3-initiated transcripts represented only 11% +/- 3%. In addition, the proportion of transcripts initiated at start site 4 was about twofold greater in liver than in bone cells (32% +/- 7% compared to 16% +/- 8%). However, expression of full-length transcripts was similar in both tissues. The distribution in osteoblastic cells reflected that in whole bone. These results demonstrate that the IGF-I transcript profile in bone cells differs to that in liver cells. Since the mRNA variants exhibit different properties, including half-life and translatability, such cell-specific variation in their relative expression is likely to reflect differential regulation of IGF-I in these tissues.
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PMID:Expression of insulin-like growth factor I (IGF-I) mRNA variants in rat bone. 883 Sep 86

In the present studies we examined the regulation of insulin-like growth factor I (IGF-I) expression in porcine granulosa cells in vitro. Using Northern analysis and ribonuclease protection assays with exon-specific probes, we identified the IGF-I messenger RNA (mRNA) transcripts present in these cells under basal and hormone-stimulated conditions. We also assessed changes in secreted IGF-I using Western blots and correlated the change in protein secretion after hormone treatment with changes in mRNA levels. By analogy to the human IGF-I gene and its transcription, two major transcripts of approximately 1 and 7.5 kilobases, seen in freshly isolated granulosa cells and follicle wall and in single passaged granulosa (MDGp1) cells, most likely correspond to IGF-IA. Minor transcripts of 3-4 kilobases, which appeared after FSH or forskolin treatments or in control cells after long exposure of the autoradiographs, were attributed to incompletely processed RNA precursors. Ribonuclease protection assay analysis using probes to detect alternative use of exon 5 or exon 6 indicated that most, if not all, of the transcripts contained only exon 6 sequence (IGF-IA). Both class 1 and class 2 transcripts were identified using exon 1- and exon 2-specific probes, respectively. GH increased steady state levels of IGF-I mRNA 3-fold, FSH increased it approximately 10-fold, and forskolin maximally increased it 12- to 15-fold. Estradiol had no effect alone or in combination with the other treatments. All treatments that increased IGF-I mRNA coordinately increased both class 1 and class 2 transcripts, with the increase in class 1 greater than that in class 2. Multiple forms of IGF-I protein were seen under basal conditions and after hormone treatment. These were identified based on mRNA analysis and biochemical methods as both glycosylated and nonglycosylated IGF-IA prohormone, incompletely processed forms of prohormone, and the mature peptide. Changes in the levels of total protein were similar to the changes in mRNA (GH, 3-fold; FSH and forskolin, 10- to 20-fold). All forms of the protein changed coordinately, suggesting that these hormones had no major effect on the intracellular processing mechanism. IGF-binding protein-3 was able to bind to all IGF-I forms. These data conclusively demonstrate FSH and GH induction of ovarian IGF-I. The porcine granulosa cell culture system used in these studies should be an excellent system for studying the hormonal regulation of IGF-I expression.
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PMID:Regulation of insulin-like growth factor I biosynthesis in porcine granulosa cells. 889 30

The transfer of cholesterol from the outer to the inner mitochondrial membrane, where side-chain cleavage occurs to form pregnenolone, is a crucial event in the regulation of steroidogenesis and recently has been demonstrated to be mediated by steroidogenic acute regulatory protein (StAR). We generated a partial porcine StAR complementary DNA (280 bp) by RT-PCR and used the corresponding antisense riboprobe to quantify the control of StAR gene expression by FSH and insulin-like growth factor I (IGF-I) in hormonally responsive swine granulosa cells, which typically manifest synergistic steroidogenic stimulation by these two dominant intrafollicular regulators. RNase protection assays were implemented to investigate the time course of the actions of FSH (100 ng/ml), IGF-I (100 ng/ml), and FSH plus IGF-I on StAR messenger RNA accumulation in serum-free cultures granulosa cells. Treatment with FSH (1.6-fold) or IGF-I (2.7-fold) alone had a small but consistent stimulatory effect on StAR message accumulation (corrected for 18S ribosomal RNA in each lane) at 48 h, whereas only IGF-I stimulated StAR protein expression (at least 6-fold as assessed by Western blot). Notably, the combined effect of FSH plus IGF-I was strongly synergistic and already significant by 24 h and maximal at 48 h (P < 0.001). Protein kinase A agonist, 8-bromoadenosine 3',5'-cAMP (8-bromo-cAMP) (1 mM) alone elicited a 3.5-fold increase in StAR message and more than 3.7-fold increase in StAR protein expression by 48 h. The combination of IGF-I and FSH or 8-bromo-cAMP evoked a 26- to 40-fold (P < 0.001) synergistic rise in StAR message accumulation. StAR protein also showed a similar synergistic pattern of expression driven by IGF-I and FSH or 8-bromo-cAMP, namely a greater than 56- to 60-fold increase. In summary, two distinct first messenger regulatory molecules, FSH and IGF-I, interact synergistically to induce amplification of StAR messenger RNA and protein expression in serum-free monolayer cultures of immature (swine) granulosa cells.
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PMID:Regulation of porcine granulosa cell steroidogenic acute regulatory protein (StAR) by insulin-like growth factor I: synergism with follicle-stimulating hormone or protein kinase A agonist. 897 33

The insulin-like growth factor I (IGF-I) gene generates by alternative splicing two IGF-I messenger RNAs (mRNAs) coding for IGF-I prehormones with different E domain sequences. In rats, these two mRNAs differ by the presence (IGF-IB) or absence (IGF-IA) of a 52-bp insert in the E domain coding region. The purpose of this study was to investigate the effect of nutritional perturbation on IGF-IA and -IB expression in rat liver. Northern blot analysis of liver mRNA revealed that the 1.5-1.9 kb and 0.9-1.2 kb IGF-I mRNA species were decreased in rats fasted for 48 h compared with either fasted-refed (48 h of each) or control-fed rats (each, P < 0.01), whereas the 7.5 kb IGF-I mRNA was decreased only when compared with the fasted-refed animals. Using semiquantitative RT-PCR, the IGF-IA transcript (114 bp amplicon) was not altered, whereas the IGF-IB transcript (166 bp amplicon) was decreased in fasted rats compared with the other two groups (both P < 0.01). We confirmed the RT-PCR results by RNase protection assay (RPA), observing that the IGF-IA (224 and 100 bases protected) was not decreased and that the IGF-IB transcript (376 bases protected), accounting for only 23% of the total IGF-I transcripts of control fed rats, was decreased by fasting. Because the results from RT-PCR and RPA do not necessarily predict full-length translatable mRNA, we subjected hepatic IGF-I transcripts to in vitro translation, and we immunoprecipitated IGF-IA and -IB prehormones. Both prehormones were translated principally from exon 1-containing mRNAs, with molecular weights of about 17K and 18K, representing 80% and 20% of the total IGF-I prehormones observed in control fed rats, respectively. Both peptides were reduced in fasted rats compared with controls (P < 0.01), and refeeding restored both. By immunoblotting of the protein extract from liver of fasted rats, IGF-IA was decreased by 77% compared with control-fed animals. Refeeding returned IGF-IA to normal. The lack of reduction of IGF-IA transcript at the alternative splice site suggests that posttranscriptional mechanisms are responsible for the reduction in steady-state IGF-I mRNAs that occurs during fasting. Additionally, we present evidence that biosynthesis of IGF-IA and -IB prehormones by liver is impaired at a posttranscriptional level.
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PMID:Effect of fasting on insulin-like growth factor (IGF)-IA and IGF-IB messenger ribonucleic acids and prehormones in rat liver. 923 57

Relaxin promotes growth of reproductive tissues, including the uterus. Although we have evidence of a role for insulin-like growth factor I (IGF-I) in mediating relaxin-induced growth of porcine granulosa cells in vitro, the mechanism of action by which relaxin enhances uterine growth has not been identified. To investigate a role for the uterine insulin-like growth factor (IGF) system in relaxin-induced uterine growth, we monitored the effects of relaxin on porcine IGFs and IGF-binding proteins (IGFBPs) in vivo. The trophic effects of relaxin on the uterus were elicited by administering relaxin or saline to prepubertal gilts every 6 h for 54 h. Three hours after the last injection, uterine flushes, uteri, follicular fluid, and ovaries were collected. Estradiol was measured in plasma and follicular fluid to confirm the prepubertal status of each animal. Significantly higher concentrations of uterine lumen IGF-I (P < 0.05) and IGF-II (P < 0.01) were observed in animals treated with relaxin. However, relaxin administration did not affect uterine IGF-I and -II gene expression, as determined by a ribonuclease protection assay and Northern analysis, respectively. In uterine flushes, relaxin treatment increased an IGFBP doublet (33 and 34.5 kDa) and IGFBP-3. The uterine IGFBP doublet was identified as IGFBP-2 by immunoprecipitation. Plasma or follicular fluid IGFs and IGFBPs were unaffected by relaxin administration. In addition, relaxin did not influence IGF-I binding to its uterine receptor. This is the first study to demonstrate regulation of the pig uterine IGF system by relaxin. In conclusion, the data point to IGF-I, IGF-II, IGFBP-2, and IGFBP-3 as putative mediators of relaxin-induced uterine growth in the pig.
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PMID:Relaxin increases insulin-like growth factors (IGFs) and IGF-binding proteins of the pig uterus in vivo. 927 49

Five days of treadmill training in rats leads to increased muscle size and running time. This was used to examine the effect of exercise on circulating insulin-like growth factor I [IGF-I; radioimmunoassay (RIA)], local muscle (hindlimb) IGF-I (by RIA), and muscle IGF-I mRNA (by ribonuclease protection assay). Eight-week-old female Sprague-Dawley rats were divided into three groups: control (n = 10); single-exercise test (n = 10), untrained but with one maximal exercise test at the end of the study; and training (n = 16), trained for 5 days and one maximal exercise test on day 6. There were no differences among the groups with respect to circulating IGF-I. Muscle IGF-I protein in trained rats (4.2 +/- 1.5 ng/g of muscle tissue) was significantly greater than both control (0.27 +/- 0.1 ng/g) and single-exercise test (0.62 +/- 0.19 ng/g, P < 0.05 by analysis of variance). There was no difference among the groups in IGF-I mRNA gene expression. These data suggest that there is an early, marked, local muscle increase in IGF-I protein in response to exercise. This increase, however, may not be related to increased muscle IGF-I gene expression. Moreover, the IGF-I response was probably local in nature since it was not matched by any increase in circulating IGF-I.
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PMID:Increase in muscle IGF-I protein but not IGF-I mRNA after 5 days of endurance training in young rats. 936 24


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