Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The conversion of androgens to estrogens by aromatase cytochrome P450 (P450arom) is an important step in the mechanism of androgen action in the brain. However, the distribution of P450arom mRNA in adult rhesus monkey brains has not been studied because specific probes have not been available. To address this deficit, we cloned and sequenced a 455-basepair segment of the 5' coding region of the rhesus P450arom cDNA. Total RNA was extracted from a rhesus monkey placenta (Day 47 of gestation and subjected to reverse transcriptase (RT) polymerase chain reaction (PCR) using consensus oligonucleotide primers selected from published human and rat P450arom DNA sequences. The RT-PCR product was subcloned into a vector and sequenced. The monkey P450arom cDNA was 97% identical to the human sequence but shared only 86% homology with the rat sequence. We then developed a ribonuclease protection assay using a monkey P450arom cDNA and studied the distribution of P450arom mRNA in adult monkey brains. This assay protected two RNA fragments, one 455 nucleotides (nt) in length and the second approximately 300 nt. The relative distribution of P450arom mRNA (the 455-nt fragment) between brain areas of the adult (n = 3) was high in the bed nucleus of the stria terminalis > medial preoptic/anterior hypothalamus > amygdala; intermediate in the medial basal hypothalamus (infundibular nucleus, median eminence, ventromedial nucleus) > lateral preoptic/anterior hypothalamus; and low in the septum > lateral-dorsal-medial hypothalamus. P450arom mRNA was undetectable in cingulate and parietal cortex, hippocampus, and cerebellum. P450arom activity, as measured by the 3H2O assay, correlated well with the distribution of P450arom mRNA (the 455-nt protected fragment; r = 0.9) in the same tissues. A shorter protected RNA fragment was found in the medial basal hypothalamus, the bed nucleus of the stria terminalis, the amygdala, and the cingulate and parietal cortex but not in the other brain areas investigated. Its presence did not correlate with aromatase activity in brain tissue. This study describes the development of a ribonuclease protection assay using a monkey cDNA produced by RT-PCR and its usefulness for studying the distribution of P450arom mRNA in brains of nonhuman primates.
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PMID:Distribution of aromatase cytochrome P450 messenger ribonucleic acid in adult rhesus monkey brains. 931 79

Brain aromatase plays an important role in the regulation of adult reproductive behavior in male rodents. This report focuses on recent experiments from our laboratory that examined the distribution and regulation of aromatase mRNA in the rat brain. Aromatase mRNA was measured by a highly sensitive ribonuclease protection assay using a 32P-labeled antisense RNA probe that was complimentary to the 5' coding region of rat aromatase mRNA. This probe protects two RNA fragments in rat brain tissue: a 430-nt length fragment and a shorter 300-nt fragment. The presence of the 300-nt RNA fragment is not associated with enzyme activity in the rat brain and appears to represent an alternative brain-specific aromatase transcript whose function, if any, is unknown. In contrast, the 430-nt RNA fragment represents mRNA, which is thought to encode functional aromatase enzyme because its levels are correlated with aromatase activity concentrations in preoptic area, hypothalamus, amygdala, and ovary. Aromatase activity and mRNA levels in the preoptic area and hypothalamus decreased by 7 days after castration and were maintained at intact levels by treatment with testosterone and dihyhdrotestosterone, but not with estradiol. In contrast, neither aromatase activity nor mRNA levels in the amygdala are affected by castration or hormone replacement. In addition, sex differences in the regulation of aromatase mRNA were apparent in both the preoptic area and hypothalamus. These results demonstrate that androgens regulate the transcription or stability of aromatase mRNA in specific brain areas. Moreover, they suggest that gender differences in androgen responsiveness play an important role in regulating gene expression in the adult rat brain.
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PMID:Regulation of aromatase gene expression in the adult rat brain. 937 Jan 99

Human adipose tissue is known to have 17 beta-oxidoreductase activity, interconverting estrone (E1) and estradiol (E2), as well as androstenedione (A) and testosterone (T). We examined both the subcutaneous abdominal and intra-abdominal (visceral) adipose tissue of women for expression of types 1, 2, and 3 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) using ribonuclease (RNase) protection assay and RT-PCR/Southern blotting. Type 1 17 beta-HSD, which encodes the enzyme responsible for the conversion of E1 to E2 in the placenta and ovary, was expressed in the subcutaneous abdominal and intra-abdominal adipose tissue of women, but the messenger RNA transcripts were predominantly incompletely spliced and therefore unlikely to encode an active protein. A pseudogene for type 1 17 beta-HSD was also expressed in these tissues, but messenger RNA transcripts were again unspliced. Type 2 17 beta-HSD, which encodes an enzyme that can catalyze the conversion of T to A and E2 to E1, was expressed in both the subcutaneous abdominal and intra-abdominal adipose tissue of women. Type 3 17 beta-HSD was also expressed in adipose tissue from both sites studied. Type 3 17 beta-HSD encodes the enzyme that catalyzes the conversion of A to T in the testis and also converts E1 to E2. Together with aromatase, which is known to be expressed in adipose tissue, the expression of types 2 and 3 17 beta-HSD indicates that sex steroid production in the adipose tissue of women is a complex process. The association of visceral obesity with the development of insulin resistance and dyslipidaemia raises the question of the role of steroid production in adipose tissue in the pathogenesis of these disorders.
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PMID:Expression of types 1, 2, and 3 17 beta-hydroxysteroid dehydrogenase in subcutaneous abdominal and intra-abdominal adipose tissue of women. 943 39

Increased extraglandular aromatization has been reported as the cause of familial gynecomastia. We studied a kindred with aromatase excess inherited in an autosomal dominant manner, in which affected males had heterosexual precocity and/or gynecomastia, and affected females had isosexual precocity and/or macromastia. The propositus was a 9-yr-old boy with gynecomastia. His 7.5-yr-old sister had precocious puberty, and their father and paternal grandmother had peripubertal gynecomastia and macromastia, respectively. Serum concentrations of gonadal and adrenal steroid hormones were determined before and after the administration of corticotropin and/or hCG. Aromatase activity was determined by [3H]delta4-androstenedione to [3H]estrone conversion by cultured skin fibroblasts and/or Epstein-Barr virus-transformed lymphocytes and was detected by immunohistochemistry and/or Western analysis. Linkage was examined with a polymorphism of the aromatase (P450arom) gene. The P450arom messenger ribonucleic acid was analyzed by rapid amplification of complementary DNA (cDNA) ends, ribonuclease protection assay, and RT-PCR. hCG testing demonstrated a high rate of conversion of delta4-androstenedione to estrone and of testosterone to estradiol in the propositus and his father. Treatment of the propositus and his sister was initiated with an aromatase inhibitor (testolactone) and a GnRH analog, which successfully delayed skeletal and pubertal development in both children. Markedly increased aromatase activity was found in the patients' fibroblasts and Epstein-Barr virus-transformed lymphocytes. The P450arom polymorphism segregated with the disease in the family. A new 5'-splice variant was present in the patients' P450arom messenger ribonucleic acid, thus identifying yet another first exon of this gene, which appears to be aberrantly expressed in this family. In conclusion, a family with the aromatase excess syndrome is described, in which the condition was inherited in an autosomal dominant manner, led to feminizing manifestations in both sexes, and was associated with the aberrant utilization of a novel transcript of the P450arom gene.
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PMID:The aromatase excess syndrome is associated with feminization of both sexes and autosomal dominant transmission of aberrant P450 aromatase gene transcription. 954 66

We demonstrated previously that testosterone regulates aromatase activity in the anterior/dorsolateral hypothalamus of male rhesus macaques. To determine the level of the androgen effect, we developed a ribonuclease protection assay to study the effects of testosterone or dihydrotestosterone (DHT) on aromatase (P450(AROM)) mRNA in selected brain areas. Adult male rhesus monkeys were treated with testosterone or DHT. Steroids in serum were quantified by RIA. Fourteen brain regions were analyzed for P450(AROM) mRNA. Significant elevations of its message over controls (P<0.05) were found in the medial preoptic area/anterior hypothalamus of both androgen treatment groups and the medial basal hypothalamus of the testosterone-treated males. Other brain areas were not affected by androgen treatment. We conclude that testosterone and DHT regulate P450(AROM) mRNA in brain regions that mediate reproductive behaviors and gonadotropin release. The P450(AROM) mRNA of other brain areas is not androgen dependent. Brain-derived estrogens may also be important for maintaining neural circuitry in brain areas not related to reproduction. The control of P450(AROM) mRNA in these areas may differ from what we report here, but it is equally important to understand the function of in situ estrogen formation in these areas.
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PMID:Region-specific regulation of cytochrome P450 aromatase messenger ribonucleic acid by androgen in brains of male rhesus monkeys. 1081 87

In vertebrates, the growth and maturation of the ovarian follicle is dependent on the appropriate dynamics of sex steroid secretion, which is dictated by gene expression of the steroidogenic enzymes. The molecular aspects of steroid regulation are poorly understood in fishes, so as a first step we determined the pattern of expression of four key steroidogenic genes throughout the ovarian cycle in an annually spawning teleost, the channel catfish (Ictalurus punctatus). The abundance of transcripts encoding 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and cholesterol side chain cleavage (P450(scc)), 17 alpha-hydroxylase/lyase (P450(c17)), and aromatase (P450(arom)) were determined by rtqRT-PCR or ribonuclease protection assay and correlated to ovarian growth and plasma titers of estradiol (E(2)) and testosterone (T) in two populations of catfish. Elevations in transcript abundance for P450(c17), P450(scc), and P450(arom) were observed at the onset of ovarian recrudescence and during early vitellogenic growth of the oocytes; however, all three decreased precipitously with the completion of vitellogenesis. Changes in the expression of these genes strongly suggest a direct correlation to E(2) and T titers. Alternatively 3 beta-HSD transcript abundance was relatively stable throughout the year. This study suggests that the genes encoding the three steroidogenic cytochrome P450s have a similar regulatory mechanism.
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PMID:Changes in the expression of genes encoding steroidogenic enzymes in the channel catfish (Ictalurus punctatus) ovary throughout a reproductive cycle. 1109 Apr 35

To understand the role of estrogen in testicular and epididymal function of rhesus monkeys, we measured steroids in the spermatic and peripheral venus circulation and aromatase activity and its mRNA in testis and epididymis. Testosterone, estradiol-17beta, and estrone, but not androstenedione, were elevated in the spermatic vein serum compared to the peripheral circulation. Aromatase activity in testis and in caput epididymis (259+/-16 [SEM] vs 274+/-47 fmol of 3H2O/mg of protein/h [n = 10], respectively) was significantly higher (p < 0.01) than in corpus and cauda (124+/-28 and 113+/-33 fmol of 3H2O/mg of protein/h [n = 10], respectively). In the ribonuclease protection assay, two P450arom mRNA transcripts were identified in testis and epididymis. One corresponded with the aromatase full-length transcript and the other was a truncated isoform. The latter was significantly more abundant than the former (p < 0.01). Our results demonstrate that the monkey testis and, to a lesser extent, the epididymis can aromatize androgens. However, in the epididymis, like in some areas of the brain, there was a discrepancy between the aromatase activity and the mRNA. The fact that P450arom mRNA and aromatase activity do not correlate in the epididymis may indicate that aromatase activity is not strictly regulated at the level of RNA expression and that other mechanisms for this regulation should be considered.
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PMID:Cytochrome P450 aromatase in testis and epididymis of male rhesus monkeys. 1182 22