Dietary and Hormonal Factors Affecting the mRNA Level of IGF-I in Rat Liver in vivo and in Primary Cultures of Rat Hepatocytes

The distribution of CuZn superoxide dismutase (SOD) molecules in subcellular organelles in rat liver hepatocytes was studied using integrated biochemical, stereological, and quantitative immunocytochemical techniques. A known concentration of purified CuZn SOD in 10% gelatin was embedded alongside the liver tissue for the calculation of CuZn SOD concentrations in hepatocyte organelles and total CuZn SOD in the rat liver. Most of the CuZn SOD was located in the cytoplasmic matrix (73.1%) and in the nucleus (11.9%) with concentrations of 1.36 and 0.71 mg/cm3, respectively. Lysosomes contained the highest concentration (5.81 mg/cm3). Only low concentrations were measured in mitochondria (0.21 mg/cm3). Membrane-bound spaces of rough endoplasmic reticulum (ER), smooth ER, and the Golgi system did not contain significant concentrations of the enzyme. By adding up the concentrations in all subcellular compartments, a total liver content of CuZn SOD was established from the immunocytochemical measurements (0.386 +/- 0.028 mg/gm liver) that agreed closely with those obtained by biochemical assays (0.380 +/- 0.058 mg/gm liver). The average distances between two CuZn SOD molecules can be calculated from enzyme concentrations. It was determined that CuZn SOD molecules in the cytoplasmic matrix and nucleus were 34 and 42 nm apart, respectively. In peroxisomes and mitochondria, average intermolecular distance increased to approximately 60 nm and increased to 136 nm in smooth ER. CuZn SOD is a relatively abundant protein in the cytosol of hepatocytes and its distribution overlaps with major sites of O2- production. The efficiency of protection CuZn SOD can provide to cytosolic proteins from attacks by superoxide anion depends on the rate of O2- production, distribution of CuZn SOD relative to cytosolic proteins, and the relative reaction rates between O2- with both cytosolic proteins and CuZn SOD. Future studies of these substrate-enzyme relationships in vivo can lead to a greater understanding of how cells handle oxidant stress.

Download Full-text

Comparison of hepatocarcinogen-induced gene expression profiles in conventional primary rat hepatocytes with in vivo rat liver

Archives of Toxicology ◽

10.1007/s00204-012-0847-x ◽

2012 ◽

Vol 86 (9) ◽

pp. 1399-1411 ◽

Cited By ~ 13

Author(s):

Tatyana Y. Doktorova ◽

Heidrun Ellinger-Ziegelbauer ◽

Mathieu Vinken ◽

Tamara Vanhaecke ◽

Joost van Delft ◽

...

Keyword(s):

Gene Expression ◽

Rat Liver ◽

Expression Profiles ◽

Gene Expression Profiles ◽

Rat Hepatocytes ◽

Primary Rat Hepatocytes

Download Full-text

Cloning and expression of the rat liver cDNA for peroxisomal enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase in gammaGT11. Transcriptional regulation of enzyme activity by Wy-14643 in primary cultures of rat hepatocytes

European Journal of Biochemistry ◽

10.1111/j.1432-1033.1987.tb13511.x ◽

1987 ◽

Vol 166 (2) ◽

pp. 273-278 ◽

Cited By ~ 18

Author(s):

Bandana CHATTERJEE ◽

C. V. Ramana MURTY ◽

Michael J. OLSON ◽

Arun K. ROY

Keyword(s):

Enzyme Activity ◽

Transcriptional Regulation ◽

Rat Liver ◽

Primary Cultures ◽

Rat Hepatocytes ◽

Cloning And Expression ◽

Hydroxyacyl Coa Dehydrogenase ◽

Regulation Of Enzyme Activity ◽

Enoyl Coa Hydratase

Download Full-text

Insulin-like growth factor I receptors in adult rat liver: characterization and in vivo regulation

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1990.258.2.e329 ◽

1990 ◽

Vol 258 (2) ◽

pp. E329-E337 ◽

Cited By ~ 1

Author(s):

N. Venkatesan ◽

M. B. Davidson

Keyword(s):

Growth Factor ◽

Rat Liver ◽

Structural Changes ◽

Electrophoretic Analysis ◽

Binding Activity ◽

Female Rats ◽

Insulin Like Growth Factor ◽

Adult Rat ◽

Igf I

Although the presence of significant amounts of insulin-like growth factor (IGF)-I receptors in fetal tissues is well documented, adult liver has been reported to contain little or no IGF-I binding activity. In the present investigation, substantial amounts of specific IGF-I receptors were detected in crude membrane fractions and in partially purified receptor preparations of female adult rat liver. Insulin was 100 times less potent than IGF-I in competing for 125I-IGF-I binding. IGF-I binding activity was much less than that of insulin binding in both the microsomal fraction and partially purified receptor preparations. Affinity cross-linking of 125I-IGF-I to purified receptors and microsomal fractions followed by electrophoretic analysis under nonreducing conditions revealed labeling of proteins with relative molecular weight (Mr) of 350,000 and 210,000-220,000, corresponding to the molecular mass of the intact tetramer and alpha-beta dimers, respectively. Under reducing conditions, the labeling of proteins with Mr of 130,000 and 260,000, corresponding to the alpha-subunit of IGF-I receptor and its dimer, respectively, was observed. Treatment of microsomes as well as partially purified receptors with 0.5-1 mM dithiothreitol resulted in decreased IGF-I binding, and this correlated with structural changes in the receptor as detected by affinity labeling and electrophoretic analysis. Hepatic IGF-I binding activity was significantly diminished in female rats exposed to chronic growth hormone excess, suggesting down-regulation of IGF-I receptors by the enhanced circulating levels of IGF-I in these animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text

Modulation of 11β-Hydroxysteroid Dehydrogenase Isozymes by Growth Hormone and Insulin-Like Growth Factor: In Vivo and In Vitro Studies1

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem.84.11.6108 ◽

1999 ◽

Vol 84 (11) ◽

pp. 4172-4177 ◽

Cited By ~ 2

Author(s):

J. S. Moore ◽

J. P. Monson ◽

G. Kaltsas ◽

P. Putignano ◽

P. J. Wood ◽

...

Keyword(s):

Growth Factor ◽

Reductase Activity ◽

Primary Cultures ◽

Inverse Correlation ◽

Hydroxysteroid Dehydrogenase ◽

Insulin Like Growth Factor ◽

Igf I ◽

Glucose Output

The interconversion of hormonally active cortisol (F) and inactive cortisone (E) is catalyzed by two isozymes of 11β-hydroxysteroid dehydrogenase (11βHSD), an oxo-reductase converting E to F (11βHSD1) and a dehydrogenase (11βHSD2) converting F to E. 11βHSD1 is important in mediating glucocorticoid-regulated glucose homeostasis and regional adipocyte differentiation. Earlier studies conducted with GH-deficient subjects treated with replacement GH suggested that GH may modulate 11βHSD1 activity. In 7 acromegalic subjects withdrawing from medical therapy (Sandostatin-LAR; 20–40 mg/month for at least 12 months), GH rose from 7.1 ± 1.5 to 17.5 ± 4.3 mU/L (mean ± se), and insulin-like growth factor I (IGF-I) rose from 43.0 ± 8.8 to 82.1 ± 13.7 nmol/L (both P < 0.05) 4 months after treatment. There was a significant alteration in the normal set-point of F to E interconversion toward E. The fall in the urinary tetrahydrocortisols/tetrahydocortisone ratio (THF+allo-THF/THE; 0.82 ± 0.06 to 0.60 ± 0.06; P < 0.02) but unaltered urinary free F/urinary free E ratio (a marker for 11βHSD2 activity) suggested that this was due to inhibition of 11βHSD1 activity. An inverse correlation between GH and the THF+allo-THF/THE ratio was observed (r = −0.422; P < 0.05). Conversely, in 12 acromegalic patients treated by transsphenoidal surgery (GH falling from 124 ± 49.2 to 29.3 ± 15.4 mU/L; P < 0.01), the THF+allo-THF/THE ratio rose from 0.53 ± 0.06 to 0.63 ± 0.07 (P < 0.05). Patients from either group who failed to demonstrate a change in GH levels showed no change in the THF+allo-THF/THE ratio. In vitro studies conducted on cells stably transfected with either the human 11βHSD1 or 11βHSD2 complementary DNA and primary cultures of human omental adipose stromal cells expressing only the 11βHSD1 isozyme indicated a dose-dependent inhibition of 11βHSD1 oxo-reductase activity with IGF-I, but not GH. Neither IGF-I nor GH had any effect on 11βHSD2 activity. GH, through an IGF-I-mediated effect, inhibits 11βHSD1 activity. This reduction in E to F conversion will increase the MCR of F, and care should be taken to monitor the adequacy of function of the hypothalamo-pituitary-adrenal axis in acromegalic subjects and in GH-deficient, hypopituitary patients commencing replacement GH therapy. Conversely, enhanced E to F conversion occurs with a reduction in GH levels; in liver and adipose tissue this would result in increased hepatic glucose output and visceral adiposity, suggesting that part of the phenotype currently attributable to adult GH deficiency may be an indirect consequence of its effect on tissue F metabolism via 11βHSD1 expression.

Download Full-text