scholarly journals The influence of starvation and tryptophan administration on the metabolism of phenylalanine, tyrosine and tryptophan in isolated rat liver cells

1984 ◽  
Vol 221 (2) ◽  
pp. 431-438 ◽  
Author(s):  
M Salter ◽  
J C Stanley ◽  
M J Fisher ◽  
C I Pogson
Keyword(s):  
Enzyme Activity ◽  
Phenylalanine Hydroxylase ◽  
Tyrosine Aminotransferase ◽  
Liver Cells ◽  
Kinetic Properties ◽  
Sprague Dawley ◽  
Cell Extracts ◽  
Sprague Dawley Rats ◽  
Rat Liver Cells ◽  
Cellular Dna

Liver cells from fed Sprague-Dawley rats metabolized phenylalanine, tyrosine and tryptophan at rates consistent with the known kinetic properties of the first enzymes of each pathway. Starvation of rats for 48 h did not increase the maximal activities of phenylalanine hydroxylase, tryptophan 2,3-dioxygenase and tyrosine aminotransferase in liver cell extracts, when results were expressed in terms of cellular DNA. Catabolic flux through the first two enzymes was unchanged; that through the aminotransferase was elevated relatively to enzyme activity. This is interpreted in terms of changes in the concentrations of 2-oxoglutarate and glutamate. Cells from tryptophan-treated animals exhibited significant increases in the catabolism of tyrosine and tryptophan, but not of phenylalanine. The activities of tyrosine aminotransferase and tryptophan 2,3-dioxygenase were also increased, although the changes in flux and enzyme activity did not correspond exactly. These results are discussed with reference to the control of aromatic amino acid catabolism in liver; the role of substrate concentration is emphasized.

scholarly journals Streptozotocin-induced diabetes impairs Mg2+ homeostasis and uptake in rat liver cells

2004 ◽  
Vol 286 (2) ◽  
pp. E184-E193 ◽  
Author(s):  
Theresa E. Fagan ◽  
Christie Cefaratti ◽  
Andrea Romani
Keyword(s):  
Liver Cells ◽  
Atp Content ◽  
Sprague Dawley ◽  
Uptake Mechanism ◽  
Diabetes Onset ◽  
Kinase C ◽  
Sprague Dawley Rats ◽  
Rat Liver Cells ◽  
Streptozotocin Induced Diabetes ◽  
Stimulation Of

Male Sprague-Dawley rats rendered diabetic by streptozotocin injection presented 10 and 20% decreases in total hepatic Mg2+ content at 4 and 8 wk, respectively, following diabetes onset. This decrease was associated with a parallel decrease in K+ and ATP content and an increase in Na+ level. In diabetic liver cells, the Mg2+ extrusion elicited by α1-adrenoceptor stimulation was markedly reduced compared with nondiabetic livers, whereas that induced by β-adrenoceptor stimulation was unaffected. In addition, diabetic hepatocytes did not accumulate Mg2+ following stimulation of protein kinase C pathway by vasopressin, diacylglycerol analogs, or phorbol 12-myristate 13-acetate derivates despite the reduced basal content in cellular Mg2+. Experiments performed in purified plasma membrane from diabetic livers located the defect at the level of the bidirectional Na+/Mg2+ exchanger operating in the basolateral domain of the hepatocyte cell membrane, which could extrude but not accumulate Mg2+ in exchange for Na+. The impairment of Mg2+ uptake mechanism, in addition to the decrease in cellular ATP level, can contribute to explaining the decrease in liver Mg2+ content observed under diabetic conditions.

scholarly journals Phosphopeptide analysis of phenylalanine hydroxylase isolated from liver cells exposed to hormonal stimuli

1986 ◽  
Vol 233 (2) ◽  
pp. 507-511 ◽  
Author(s):  
M J Fisher ◽  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Phenylalanine Hydroxylase ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Liver Cells ◽  
Hormonal Control ◽  
Ionophore A23187 ◽  
Peptide Fragments ◽  
Cell Extracts ◽  
Rat Liver Cells ◽  
Phosphopeptide Analysis

Hormonal control of the phosphorylation of phenylalanine hydroxylase was studied by using rat liver cells incubated with [32P]Pi. After immunoprecipitation from cell extracts, the hydroxylase was subjected to proteinase digestion and subsequent sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. V8-proteinase digestion yielded one major 32P-labelled fragment, of approx. 9 kDa. Chymotrypsin digestion gave five 32P-labelled fragments ranging from approx. 39 kDa to approx. 10 kDa. Noradrenaline (10 microM) and glucagon (0.1 microM) enhanced the 32P content of all peptide fragments uniformly. Phorbol ester, in contrast with ionophore A23187, did not stimulate enzyme phosphorylation or enhance phenylalanine metabolism in liver cells. These results are discussed in relation to the nature of the protein kinase(s) that mediate phosphorylation of phenylalanine hydroxylase in liver cells.

Enzymatic condensation of dopamine and acetaldehyde: a salsolinol synthase from rat brain

Biologia ◽  
2011 ◽  
Vol 66 (6) ◽  
Author(s):  
Xuechai Chen ◽  
Abida Arshad ◽  
Hong Qing ◽  
Rui Wang ◽  
Jianqing Lu ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Substantia Nigra ◽  
Human Subjects ◽  
Enzymatic Reaction ◽  
Brain Regions ◽  
Activity Detection ◽  
Reaction Products ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Salsolinol Synthase

AbstractSalsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline; Sal) is structurally similar to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which is supposed to have a role in the development of Parkinson-like syndrome in both human and non-human subjects. In the human brain, the amount of (R)-enantiomer of Sal is much higher than (S)-enantiomer, suggesting that a putative enzyme may participate in the synthesis of (R)-salsolinol, called (R)-salsolinol synthase. In this study, the (R)-salsolinol synthase activity in the condensation of dopamine and acetaldehyde was investigated in the crude extracts from the brains of Sprague Dawley rats. Identification of the enzymatic reaction products and enzyme activity detection were achieved by HPLC-electrochemical detection. The discovery of this enzyme activity in rat’s brain indicates the natural existence of (R)-salsolinol synthase in the brains of humans and rats, and it is distributed in most brain regions of rat with higher activity in soluble proteins extracted from striatum and substantia nigra.

Factors affecting induction of tyrosine aminotransferase in isolated rat liver cells

1981 ◽  
Vol 34 (1) ◽  
pp. 59-64 ◽  
Author(s):  
Fiona A. O. Marston ◽  
Alan J. Dickson ◽  
Christopher I. Pogson
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Liver Cells ◽  
Factors Affecting ◽  
Isolated Rat Liver ◽  
Rat Liver Cells ◽  
Isolated Rat

scholarly journals Dietary soy-phytoestrogens decrease testosterone levels and prostate weight without altering LH, prostate 5alpha-reductase or testicular steroidogenic acute regulatory peptide levels in adult male Sprague-Dawley rats

2001 ◽  
Vol 170 (3) ◽  
pp. 591-599 ◽  
Author(s):  
KS Weber ◽  
KD Setchell ◽  
DM Stocco ◽  
ED Lephart
Keyword(s):  
Enzyme Activity ◽  
Locomotor Activity ◽  
Plasma Testosterone ◽  
Sprague Dawley ◽  
Regulatory Peptide ◽  
Hormone Levels ◽  
Prostate Weight ◽  
Sprague Dawley Rats ◽  
Short Period ◽  
Steroidogenic Acute Regulatory

Nutritional factors, especially phytoestrogens, have been extensively studied for their potential beneficial effects against hormone-dependent and age-related diseases. The present study describes the short-term effects of dietary phytoestrogens on regulatory behaviors (food/water intake, locomotor activity and body weight), prostate weight, prostate 5alpha-reductase enzyme activity, reproductive hormone levels, and testicular steroidogenic acute regulatory peptide (StAR) levels in adult Sprague-Dawley rats. Animals were fed either a phytoestrogen-rich diet containing approximately 600 microg/g isoflavones (as determined by HPLC) or a phytoestrogen-free diet. After 5 weeks of consuming these diets, plasma phytoestrogen levels were 35 times higher in animals fed the phytoestrogen-rich vs phytoestrogen-free diets. Body and prostate weights were significantly decreased in animals fed the phytoestrogen-rich diet vs the phytoestrogen-free fed animals; however, no significant change in prostate 5alpha-reductase enzyme activity was observed between the treatment groups. Locomotor activity levels were higher in the phytoestrogen-rich vs the phytoestrogen-free animals during the course of the treatment interval. Plasma testosterone and androstenedione levels were significantly lower in the animals fed the phytoestrogen-rich diet compared with animals fed the phytoestrogen-free diet. However, there were no significant differences in plasma LH or estradiol levels between the diet groups. Testicular StAR levels were not significantly different between the phytoestrogen-rich vs the phytoestrogen-free fed animals. These results indicated that consumption of dietary phytoestrogens resulting in very high plasma isoflavone levels over a relatively short period can significantly alter body and prostate weight and plasma androgen hormone levels without affecting gonadotropin or testicular StAR levels. The findings of this study identify the biological actions of phytoestrogens on male reproductive endocrinology and provide insights into the protective effects these estrogen mimics exert in male reproductive disorders such as benign prostatic hyperplasia and prostate cancer.

Effect of the antiglucocorticoid RU486 on adrenal steroidogenic enzyme activity and steroidogenesis

1994 ◽  
Vol 130 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Barry D Albertson ◽  
R Blake Hill ◽  
Kellie A Sprague ◽  
Karen E Wood ◽  
Lynnette K Nieman ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Cynomolgus Macaque ◽  
Sprague Dawley ◽  
Steroidogenic Enzyme ◽  
Monkey Model ◽  
Ectopic Secretion ◽  
Adrenal Steroidogenesis ◽  
Sprague Dawley Rats

Albertson BD, Hill RB, Sprague KA, Wood KE, Nieman LK, Loriaux DL. Effect of the antiglucocorticoid RU486 on adrenal steroidogenic enzyme activity and steroidogenesis. Eur J Endocrinol 1994;130: 195–200. ISSN 0804–4643 RU486, a synthetic steroid receptor antagonist, has strong antiprogesterone and antiglucocorticoid properties. Chronic RU486 administration in two patients with ectopic secretion of adrenocorticotropin (ACTH) has been associated with decreasing plasma cortisol concentrations. One explanation of this finding is that RU486 may directly inhibit adrenal steroidogenesis. To test this hypothesis, we measured the effect of RU486 on specific steroidogenic enzymatic steps using an in vivo rat and an in vitro monkey model. Hypophysectomized–castrated–ACTH-replaced Sprague-Dawley rats were given RU486 i.p. at daily doses of 0, 0.0005, 0.005, 0.05, 0.5 and 5 mg/kg body weight per day for 7 days. The animals were sacrificed, and blood and adrenal glands collected. Adrenal cortical mitochondria and microsomes were purified from the rats and from two untreated Cynomolgus macaque monkeys. Specific steroidogenic enzyme activities were measured in the rat by the incorporation of 14C-labeled steroid substrates into products. A similar protocol was used to assay the steroidogenesis in the monkey adrenal fractions in the presence and absence of added RU486. Although rat adrenal weights decreased significantly at the highest RU486 dose, plasma levels of corticosterone were similar in control and treated rats. Rat adrenal 3β-hydroxysteroid dehydrogenase/isomerase (3-HSD), 21-hydroxylase (21-OH) and 11-hydroxylase (11-OH) activities decreased with increasing RU486 doses, with 21-OH and 11-OH being most severely affected. Monkey adrenal 3-HSD, 21-OH, 11-OH, 1 7-hydroxylase and 17,20-desmolase similarly decreased in the presence of increasing in vitro concentrations of RU486. Taken together, these results suggest that RU486 directly inhibits adrenal steroidogenesis, with a locus of action at several key enzymatic steps in the glucocorticoid pathway. This steroidogenic blockade may account for the observed decreases in glucocorticoids during RU486 treatment. Lynette K Nieman, Developmental Endocrinology Branch, NICHD, Building 10, Room 10N262, NIH, Bethesda, MD 20892, USA

Mechanism of induction of mucosal ornithine decarboxylase by food

1986 ◽  
Vol 251 (3) ◽  
pp. G370-G374 ◽  
Author(s):  
K. Tabata ◽  
L. R. Johnson
Keyword(s):  
Enzyme Activity ◽  
Ornithine Decarboxylase ◽  
Fold Increase ◽  
Enzyme Activation ◽  
Gut Contents ◽  
Sprague Dawley ◽  
Direct Stimulation ◽  
Sprague Dawley Rats ◽  
Fasted Rats ◽  
Stimulation Of

Refeeding fasted rats dramatically increases ornithine decarboxylase (ODC) activity in the mucosa of the small intestine and colon. The agents responsible for that activation and pathways leading to activation, however, have not been identified. The current work examines whether stimulation of ODC activity is mediated humorally or directly and whether dietary amines might be in part responsible for activation. Male Sprague-Dawley rats were used 1 wk after they were surgically prepared with Thiry-Vella jejunal loops. Two hours after refeeding rats fasted for 48 h, ODC activity increased 40-fold in mucosa from the intact jejunum and 4-fold in the mucosa of the bypassed segments. The injection of intestinal contents (obtained from additional fed rats) into the bypassed loop caused a 10-fold increase in ODC activity in the loop measured 2 h later. Injection of gut contents, lyophilized to remove dietary amines, produced no change in enzyme activity. The addition of 400 mol dimethylamine to lyophilized gut contents restored enzyme activation to 80% of the previous level. These data allow the following conclusions: following a meal mucosal ODC is activated by both humoral and direct mechanisms, direct stimulation by dietary constituents appears to be the predominant mechanism involved, and dietary amines may be one of the agents involved in directly increasing enzyme activity.

Sign in / Sign up

Export Citation Format

Share Document