Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The measurement of alterations in low abundance mRNAs such as the hypothalamic hormones luteinizing hormone-releasing hormone (LHRH) and growth hormone-releasing hormone (GHRH or GRF) from individual hypothalamic tissues in rats has previously been difficult and usually required either isolation of poly(A) mRNA or the pooling of numerous animals to obtain a reasonable signal on Northern blots. Although more sensitive detection methods exist, such as the use of RNA probes or solution hybridization (RNase protection), we have found the most reliable, sensitive, rapid, and accurate method is the reverse transcription-polymerase chain reaction (RT-PCR) using histone H3.3 as an internal control for both steps of this procedure. H3.3 is a cell-cycle independent and constitutively expressed gene in all tissues. We have developed an RT-PCR assay for LHRH and GRF mRNA quantitation and comparative analysis for hypothalamic and extrahypothalamic brain tissues and present the use of RT-PCR for LHRH quantitation in ethanol (EtOH) studies.
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PMID:Coupled reverse transcription-polymerase chain reaction (RT-PCR) technique is comparative, quantitative, and rapid: uses in alcohol research involving low abundance mRNA species such as hypothalamic LHRH and GRF. 768 70

Recent studies have demonstrated that passive immunization of neonatal rats to GRF inhibited their somatic growth through the suppression of GH secretion. In this study, we investigated the changes in pituitary GRF receptor (GRFR) expression in GRF antibody (GRF-ab) treated rats. Neonatal rats were treated from day 1 to day 10 after birth with every other day sc injection of 50 microliters of normal rabbit serum (groups I: control & III) or rabbit serum containing GRF-ab (groups II & IV). In addition, groups III & IV received twice daily injection of recombinant human GH (0.4 microgram/kg, sc). The rats were sacrificed on day 11 and pituitaries were removed. The pituitary weights in all treatment groups were decreased compared to the control group (I). Total pituitary RNA was extracted and GRFR mRNA levels were determined by RNase protection assay. Receptor RNA levels were quantitated and normalized to an internal standard, glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The ratios of GRFR mRNA to GAPDH mRNA were significantly decreased to 49.6 +/- 4.9 (mean +/- SD), 73.0 +/- 8.7, 43.6 +/- 9.5% of control group I in the experimental groups II, III, and IV, respectively (P < 0.01). These data suggest that (1) suppression of GH secretion in GRF-ab treated animals was due, at least in part, to a decrease in GRFR expression, (2) GRF may be necessary for its own receptor expression, (3) exogenous administration of GH suppresses pituitary GRFR mRNA.
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PMID:Growth hormone-releasing factor (GRF) regulates expression of its own receptor. 864 Dec 20

The recently cloned leptin receptor (OB-R) is expressed in many tissues, including the anterior pituitary. It is not known whether OB-R gene expression is regulated by pituitary hormones. In the present study, we detected the long isoform of OB-R (OB-R(L)) in the anterior pituitary of normal mice using RT-PCR, but were unable to detect the short isoform (OB-R(S)). In human growth hormone-releasing hormone (hGHRH) transgenic mice, we discovered a significant increase in OB-R(L) mRNA levels in the anterior pituitary as compared to controls, and OB-R(S) gene expression was detectable. In contrast to the pituitary, there were no significant changes in OB-R gene expression for either isoform in the hypothalamus of hGHRH mice. The dramatic increase in the gene expression of OB-R(L) in the anterior pituitary of hGHRH transgenic mice was confirmed by RNase protection assay. This is the first study to demonstrate that OB-R gene expression in the anterior pituitary gland is increased by GH and/or GHRH.
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PMID:Upregulation of leptin receptor gene expression in the anterior pituitary of human growth hormone-releasing hormone transgenic mice. 942 42

We reported previously an increase in leptin receptor (OBR) gene expression in the anterior pituitary of human GH-releasing hormone (hGHRH) transgenic mice. The primary goal of this study was to investigate the possible mechanisms regulating OBR expression in these mice. Compared with normal sibling controls, hGHRH transgenic mice had significantly greater amounts of abdominal fat, higher levels of leptin messenger RNA (mRNA), and a 2-fold increase in plasma leptin concentrations. Despite normal plasma glucose levels, hGHRH transgenic mice had 4.5-fold elevated levels of plasma insulin. Using a ribonuclease protection assay, we measured the mRNA levels of the OBR long form (OBR(L)) in the anterior pituitary and hypothalamus after 48 h of fasting. In the anterior pituitary, food deprivation induced dramatic increases in OBR(L) mRNA levels in both normal and transgenic mice. In contrast, in the hypothalamus, fasting resulted in a significant decrease in OBR(L) gene expression in normal mice, and no changes were detected in hGHRH transgenic mice. Using dual in situ hybridization, OBR(L) mRNA was detected in somatotrophs. Moreover, the number of OBR(L)-positive pituitary cells as well as the percentage of OBR(L)-positive cells that express GH mRNA were increased in transgenic mice. In conclusion, 1) the modest obesity in hGHRH transgenic mice is associated with increases in leptin synthesis and secretion as well as insulin secretion; 2) GH and/or GHRH as well as leptin and insulin may differentially contribute to the changes in OBR(L) gene expression in the anterior pituitary and the hypothalamus; 3) the response of OBR(L) gene expression in the hypothalamus to fasting is absent in the modestly obese hGHRH transgenic mice; and 4) somatotrophs are target cells for leptin, and the increase in OBR(L) gene expression in the pituitary of hGHRH transgenic mice is due at least in part to the increase in the number of cells expressing OBR(L).
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PMID:The human growth hormone-releasing hormone transgenic mouse as a model of modest obesity: differential changes in leptin receptor (OBR) gene expression in the anterior pituitary and hypothalamus after fasting and OBR localization in somatotrophs. 1043 18

Growth hormone-secretagogue receptor (GHSR) RNA is known to be expressed in the hypothalamus and pituitary. Since endogenous GH secretagogue (GHS) is still unknown, the physiological role of GHS and GHSR in growth is not well understood. In this study, we have determined the effects of growth hormone in GH-releasing hormone receptor (GHRHR) and GHSR RNA expression in spontaneous Dwarf rats (SDRs) which are deficient in GH secretion, with or without GH replacement. Twenty-five-day-old SDRs received daily s.c. injection of human GH (40 microg/kg BW x 2/day) or control solution for two weeks. On day 40, the rats were sacrificed by decapitation and the pituitaries were immediately removed and quickly frozen. Total RNA was extracted from the pituitary, and mRNA coding GHSR was detected and semi-quantitated by competitive RT-PCR. Pituitaries from control SDRs showed strong GHSR RNA expression and the expression level was 5 to 10 times higher in females than in males. When GH was replaced, GHSR RNA expression greatly decreased. Pituitary GHRHR RNA expression, determined by RNase Protection Assay, was similar in male and female control animals; and was also greatly reduced in rats treated with GH when compared to the control. These results suggest that the expression of both GHSR and GHRHR is regulated by growth hormone, presumably via changes in hypothalamic GHRH and/or endogenous GHS. The apparent sexual dimorphism in GHSR indicates different regulatory effects of sex steroid in young growing SDRs.
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PMID:Regulation of pituitary growth hormone-secretagogue and growth hormone-releasing hormone receptor RNA expression in young Dwarf rats. 1089 Jan 84

To provide information about the kidney GHRH receptor (GHRH-R), we assessed its tissue and cellular localization, defined its pattern of expression in developing and aging rats, and studied the effects of GHRH on the regulation of GHRH-R mRNA levels and receptor internalization. In situ hybridization and ribonuclease protection assay demonstrated that GHRH-R mRNA is restricted to the Henle's loop (HL). GHRH-R mRNA levels were low in the medulla from 3- and 12-d-old male rats, increased significantly in that from 30- to 70-d-old rats, and decreased in that from 12- and 18-month-old animals. Compared with the GHRH-R mRNA profile obtained in the pituitary, these data support the concept of a tissue-specific regulation of GHRH-R. In HL cell cultures from 70-d-old rats, a 4-h incubation with 1-100 nM rat GHRH-(1-29)NH(2) reduced GHRH-R mRNA levels significantly. As anti-GHRH-R- (392-404) immunoreactivity was demonstrated in HL cells, internalization of [N(alpha)-5-carboxyfluoresceinyl-D-Ala(2),Ala(8), Ala(15),Lys(22)]hGHRH-(1-29)NH(2) in a time- and temperature-dependent manner and inhibition of this process by phenyl arsine oxide indicate that desensitization to GHRH involves both GHRH-R internalization and down-regulation of GHRH-R mRNA levels. Localization of a functional GHRH-R in HL and its regulation during development and aging suggest roles associated with cellular proliferation, differentiation, and/or water/electrolyte transport.
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PMID:Localization and regulation of a functional GHRH receptor in the rat renal medulla. 1189 6

In the fasted and the streptozotocin (STZ)-induced diabetic male rat, hypothalamic growth hormone (GH)-releasing hormone (GHRH) mRNA levels, and pulsatile GH release are decreased. These changes are believed to be due to a rise in hypothalamic neuropeptide Y (NPY) that inhibits GHRH expression. To directly test if NPY is required for metabolic regulation of hypothalamic neuropeptides important in GH secretion, NPY, GHRH and somatostatin (SRIH) mRNA levels were determined in fasted (48 h) and STZ-treated wild-type (NPY(+/+)) and NPY-knockout (NPY(-/-)) mice by ribonuclease protection assay. In addition, pituitary receptor mRNA levels for GHRH (GHRH-R), ghrelin (GHS-R) and SRIH (sst2) were assessed by RT-PCR. Under fed conditions the GH axis of NPY(+/+) and NPY(-/-) did not differ. In the NPY(+/+) mouse, fasting resulted in a 23% weight loss and >250% increase in NPY mRNA accompanied by a significant reduction in both GHRH and SRIH mRNA. These changes were associated with increases in pituitary expression of GHRH-R and GHS-R and a concomitant suppression of sst2. In the NPY(-/-) mouse, fasting also resulted in a 23% weight loss and comparable changes in GHRH-R and sst2, but failed to alter GHRH, SRIH and GHS-R mRNA levels. Fasting resulted in an overall increase in circulating GH, which reached significance in the fasted NPY(-/-) mouse. Induction of diabetes in NPY(+/+) mice, using a single, high-dose, STZ injection (150 mg/kg), resulted in modest weight loss (5%), and a 158% increase NPY expression which was associated with reciprocal changes in pituitary GHS-R and sst2 expression, similar to that observed in the fasted state, but no change in hypothalamic GHRH or SRIF expression was observed. Induction of diabetes in NPY(+/+) and NPY(-/-) mice, using a multiple, low-dose, STZ paradigm (5 consecutive daily injections of 40 mg/kg), did not alter body weight, hypothalamic neuropeptide expression or pituitary receptor expression, with the exception that sst2 mRNA levels were suppressed and GH levels did rise in the NPY(-/-) mouse. These observations demonstrate that NPY is not required for basal regulation of the GH axis, but is required for fasting-induced suppression of GHRH and SRIH expression, as well as fasting-induced augmentation of pituitary GHS-R mRNA. In contrast to the rat, fasting clearly did not suppress circulating GH levels in mice, but resulted in an overall rise in mean GH levels, similar to that observed in other mammalian species. The fact that many of the fasting-induced changes in the GH axis were observed in the high-dose STZ-treated mice, but were not observed in the multiple, low-dose paradigm, suggests STZ-mediated modulation of GH axis function is dependent on the severity of the catabolic state and not hyperglycemia.
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PMID:Expression analysis of hypothalamic and pituitary components of the growth hormone axis in fasted and streptozotocin-treated neuropeptide Y (NPY)-intact (NPY+/+) and NPY-knockout (NPY-/-) mice. 1624 97