Metabolism of C14-labeled substrates by rabbit kidney cortex and medulla

1962 ◽  
Vol 203 (1) ◽  
pp. 27-36 ◽  
Author(s):  
James B. Lee ◽  
Vernon K. Vance ◽  
George F. Cahill
Keyword(s):  
Fatty Acids ◽  
The Other ◽  
High Rate ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Anaerobic Conditions ◽  
Kidney Medulla ◽  
Bicarbonate Buffer ◽  
Radioactive Substrate

Slices of rabbit kidney cortex and medulla were incubated for 90 min at 38 C in Krebs-Ringer bicarbonate buffer containing C14 labeled substrate. In addition to substrate disappearance and concentrations of glycogen and fatty acids, measurements were made of the amount of radioactive substrate incorporated into CO2, glycogen, and fatty acids per gram of wet tissue. Glucose, fructose, mannose, glycerol, pyruvate, and palmitate were oxidized to a significantly greater extent by cortex than medulla. The concentration of glycogen in kidney medulla was twice that of cortex and was maintained at initial concentrations only in the presence of glucose, which showed a significantly greater incorporation into medullary glycogen than did the other substrates. Under pure anaerobic conditions simulating those in vivo, the present study suggests that the metabolism of medulla is almost exclusively glucose-dependent anaerobic glycolysis. On the other hand, the cortex is capable of utilizing a variety of substrates for a high rate of aerobic metabolism.

scholarly journals Distribution of prostaglandins in rabbit kidney

1970 ◽  
Vol 116 (3) ◽  
pp. 421-424 ◽  
Author(s):  
Keith Crowshaw ◽  
J. Z. Szlyk
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Sodium Hydroxide ◽  
Silicic Acid ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Kidney Medulla ◽  
Silicic Acid Chromatography ◽  
Before And After ◽  
Weak Activity

Three prostaglandins (PGE2, PGF2α and PGA2) are present in rabbit kidney medulla. An acidic lipid extract (0.165g) obtained from 2kg of frozen rabbit kidney cortex was separated by silicic acid chromatography to yield eluates containing fatty acids, possible non-polar prostaglandin metabolites, PGA, PGE and PGF compounds. Ultraviolet spectra of the eluates before and after treatment with sodium hydroxide did not yield chromophores typical of any known prostaglandins or related metabolites. By using more sensitive bioassay procedures (contraction of rabbit duodenum) weak activity equivalent to 60μg of PGE2 and 10μg of PGF2α was detected in the PGE and PGF eluates respectively. Extraction and bioassay of fresh kidney cortex revealed no prostaglandin-like activity. Attempts to biosynthesize prostaglandins in fresh homogenates of rabbit kidney cortex from endogenous precursors and from added arachidonic acid were unsuccessful. When freshly prepared homogenates of rabbit kidney cortex were incubated with added PGE1 no evidence of enzymic breakdown was obtained. It is concluded that rabbit kidney prostaglandins are present predominantly in the medulla and there are no cortical mechanisms for their biosynthesis or inactivation under normal conditions.

scholarly journals Overlapping Repressor Binding Sites Result in Additive Regulation of Escherichia coli FadH by FadR and ArcA

2010 ◽  
Vol 192 (17) ◽  
pp. 4289-4299 ◽  
Author(s):  
Youjun Feng ◽  
John E. Cronan
Keyword(s):  
Escherichia Coli ◽  
Fatty Acids ◽  
Cyclic Amp ◽  
Unsaturated Fatty Acids ◽  
Genetic Regulation ◽  
Receptor Protein ◽  
Anaerobic Conditions ◽  
Mobility Shift ◽  
Long Chain

ABSTRACT Escherichia coli fadH encodes a 2,4-dienoyl reductase that plays an auxiliary role in β-oxidation of certain unsaturated fatty acids. In the 2 decades since its discovery, FadH biochemistry has been studied extensively. However, the genetic regulation of FadH has been explored only partially. Here we report mapping of the fadH promoter and document its complex regulation by three independent regulators, the fatty acid degradation FadR repressor, the oxygen-responsive ArcA-ArcB two-component system, and the cyclic AMP receptor protein-cyclic AMP (CRP-cAMP) complex. Electrophoretic mobility shift assays demonstrated that FadR binds to the fadH promoter region and that this binding can be specifically reversed by long-chain acyl-coenzyme A (CoA) thioesters. In vivo data combining transcriptional lacZ fusion and real-time quantitative PCR (qPCR) analyses indicated that fadH is strongly repressed by FadR, in agreement with induction of fadH by long-chain fatty acids. Inactivation of arcA increased fadH transcription by >3-fold under anaerobic conditions. Moreover, fadH expression was increased 8- to 10-fold under anaerobic conditions upon deletion of both the fadR and the arcA gene, indicating that anaerobic expression is additively repressed by FadR and ArcA-ArcB. Unlike fadM, a newly reported member of the E. coli fad regulon that encodes another auxiliary β-oxidation enzyme, fadH was activated by the CRP-cAMP complex in a manner similar to those of the prototypical fad genes. In the absence of the CRP-cAMP complex, repression of fadH expression by both FadR and ArcA-ArcB was very weak, suggesting a possible interplay with other DNA binding proteins.

scholarly journals Stimulation of prostaglandin E2 synthesis by exogenous phospholipase A2 and C in rabbit kidney medulla slices

1984 ◽  
Vol 218 (1) ◽  
pp. 69-74 ◽  
Author(s):  
Y Fujimoto ◽  
N Akamatsu ◽  
A Hattori ◽  
T Fujita
Keyword(s):  
Fatty Acids ◽  
Prostaglandin E2 ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Unsaturated Fatty Acids ◽  
Rabbit Kidney ◽  
Dependent Manner ◽  
Kidney Medulla ◽  
Diacylglycerol Lipase ◽  
Dose Dependent

We have investigated the effects of phospholipase A2 and C on the synthesis of prostaglandin E2 in rabbit kidney medulla and the release of fatty acids from the medulla slices. Exogenous phospholipase A2 [from Naja naja (Indian cobra) venom] and phospholipase C (from Clostridium welchii) stimulated prostaglandin E2 production in a dose-dependent manner. At the maximal effective concentrations (0.5 unit of phospholipase A2/ml, 2 units of phospholipase C/ml), phospholipase C increased prostaglandin E2 formation to the level observed with phospholipase A2. Phospholipase A2 enhanced the release only of unsaturated fatty acids, whereas phospholipase C stimulated the release of individual free fatty acids (C 16:0, C 18:0, C 18:1, C 18:2 and C 20:4). Moreover, p-bromophenacyl bromide inhibited phospholipase A2-stimulated prostaglandin E2 production and the release of fatty acids, but it had no influence on prostaglandin E2 formation and the release of fatty acids increased by phospholipase C, indicating that the stimulatory effect of phospholipase C is not mediated through the activation of endogenous phospholipase A2. These results suggest the presence of diacylglycerol lipase and monoacylglycerol lipase in the kidney and the importance of this pathway in prostaglandin synthesis by the kidney.

scholarly journals Renal glycerol metabolism and the distribution of glycerol kinase in rabbit nephron

1981 ◽  
Vol 198 (3) ◽  
pp. 543-549 ◽  
Author(s):  
G Wirthensohn ◽  
A Vandewalle ◽  
W G Guder
Keyword(s):  
Glycerol Kinase ◽  
The Other ◽  
Rabbit Kidney ◽  
Glycerol Metabolism ◽  
Kidney Cortex ◽  
Collagenase Treatment ◽  
Uptake Rates ◽  
Metabolic Products ◽  
Pars Recta ◽  
Convoluted Tubules

Glycerol and dihydroxyacetone are metabolized by rabbit kidney-cortex tubules, isolated by collagenase treatment. Half-maximal concentrations of both substrates were determined with regard to uptake rates and product formations. Maximal uptake rates were 643 and 329 mumol/h per g of protein for dihydroxyacetone and glycerol respectively. Glucose and lactate were found as major metabolic products. Glycerol kinase, the enzyme catalysing the first step in renal glycerol and dihydroxyacetone metabolism, was measured radiochemically as described by Newsholme, Robinson & Taylor [(1967) Biochim, Biophys. Acta 132, 338-346] and adapted for studies of the localization of this enzyme along the different structures of rabbit nephron. The results show that glycerol kinase is located exclusively in the proximal segments, i.e. the proximal convoluted tubules and the pars recta, but is negligible in the other structures studied. The activities were close to the maximal dihydroxyacetone uptake rates measured in tubule suspensions.

scholarly journals Kidney outer medulla mitochondria are more efficient compared with cortex mitochondria as a strategy to sustain ATP production in a suboptimal environment

2018 ◽  
Vol 315 (3) ◽  
pp. F677-F681 ◽  
Author(s):  
Tomas A. Schiffer ◽  
Håkan Gustafsson ◽  
Fredrik Palm
Keyword(s):  
Oxygen Affinity ◽  
Kidney Cortex ◽  
Thick Ascending Limb ◽  
Kidney Medulla ◽  
Atp Production ◽  
Medullary Thick Ascending Limb ◽  
Functional Problem ◽  
Nephron Segment ◽  
Regional Renal Blood Flow

The kidneys receive ~25% of cardiac output, which is a prerequisite to maintain sufficient glomerular filtration rate. However, both intrarenal regional renal blood flow and tissue oxygen levels are heterogeneous with decreasing levels in the inner part of the medulla. These differences, in combination with the heterogeneous metabolic activity of the different nephron segment located in the different parts of the kidney, may constitute a functional problem when challenged. The proximal tubule and the medullary thick ascending limb of Henle are considered to have the highest metabolic rate, which is related to the high mitochondria content needed to sustain sufficient ATP production from oxidative phosphorylation to support high electrolyte transport activity in these nephron segments. Interestingly, the cells located in kidney medulla function at the verge of hypoxia, and the mitochondria may have adapted to the surrounding environment. However, little is known about intrarenal differences in mitochondria function. We therefore investigated functional differences between mitochondria isolated from kidney cortex and medulla of healthy normoglycemic rats by using high-resolution respirometry. The results demonstrate that medullary mitochondria had a higher degree of coupling, are more efficient, and have higher oxygen affinity, which would make them more suitable to function in an environment with limited oxygen supply. Furthermore, these results support the hypothesis that mitochondria of medullary cells have adapted to the normal hypoxic in vivo situation as a strategy of sustaining ATP production in a suboptimal environment.

Differential effects of selenium compounds on glucose synthesis in rabbit kidney-cortex tubules and hepatocytes. In vitro and in vivo studies

2007 ◽  
Vol 101 (3) ◽  
pp. 493-505 ◽  
Author(s):  
Anna Kiersztan ◽  
Izabela Lukasinska ◽  
Anna Baranska ◽  
Magdalena Lebiedzinska ◽  
Andrzej Nagalski ◽  
...  
Keyword(s):  
In Vivo Studies ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Selenium Compounds ◽  
Differential Effects ◽  
Glucose Synthesis

Effects of Stimulation and Inhibition of the Renal Prostaglandin Synthetase System on Renin Release in vivo and in vitro

1976 ◽  
Vol 51 (s3) ◽  
pp. 271s-274s
Author(s):  
P. C. Weber ◽  
C. Larsson ◽  
M. Hamberg ◽  
E. Änggård ◽  
E. J. Corey ◽  
...  
Keyword(s):  
Plasma Renin Activity ◽  
Plasma Renin ◽  
Renin Activity ◽  
Renin Release ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Acid Pretreatment ◽  
Prostaglandin Endoperoxide

1. The prostaglandin precursor arachidonic acid (C20:4) increases plasma renin activity in the rabbit and rat when it is infused into the renal arteries. 2. The increase in plasma renin activity after C20:4 in rats is not changed by volume expansion. 3. The inhibitor of prostaglandin synthesis indomethacin decreases plasma renin activity in the rabbit. 4. The increase in plasma renin activity after total renal ischaemia is abolished by pretreatment with indomethacin. 5. C20:4 increases dose- and time-dependent renin release from slices of rabbit kidney cortex. 6. Indomethacin or 5,8,11,14-eicosatetraynoic acid pretreatment in vivo, and addition to the incubation medium, reduces basal as well as C20:4-stimulated renin release in vitro. 7. The stimulating effect of C20:4 on renin release is assumed to be caused directly by formation of prostaglandin endoperoxides in the kidney cortex and not by prostaglandins since in vitro a natural prostaglandin endoperoxide (PGG2) and two stable synthetic prostaglandin endoperoxide analogues (EPA I and EPA II) do increase the release of renin, but PGE2 has no effect and PGF2α inhibits renin release.

scholarly journals Biosynthesis of a mycobacterial lipopolysaccharide. Incorporation of [14C]acyl groups by whole cells in vivo

1973 ◽  
Vol 132 (2) ◽  
pp. 329-340 ◽  
Author(s):  
Koyu Narumi ◽  
John M. Keller ◽  
Clinton E. Ballou
Keyword(s):  
Fatty Acids ◽  
Specific Radioactivity ◽  
Short Chain Fatty Acids ◽  
The Other ◽  
Whole Cells ◽  
Mycobacterium Phlei ◽  
Turn Over ◽  
Kinetics Of ◽  
Normal Constituent

1. Mycobacterium phlei (A.T.C.C. 356) cells were incubated with 14C-labelled short-chain fatty acids and the 6-O-methylglucose-containing lipopolysaccharides that became esterified with radioactive acyl groups were isolated. The pattern of labelling of these lipopolysaccharides with the different acyl groups, the effects of different conditions on labelling patterns, and the kinetics of the turnover of 14C-labelled acyl groups were studied. 2. The labelling patterns are summarized as follows. [1-14C]Acetate was incorporated into all of the acyl groups. [1-14C]Propionate led to labelling of propionate and succinate, while [1-14C]isobutyrate was incorporated mostly as such, along with a trace amount in iso-octanoate. 3. Under the conditions of the experiments, [1-14C]acetate was rapidly incorporated into succinyl (3-carboxypropionyl) and octanoyl groups, whereas the acetyl groups themselves were labelled more slowly. Radioactivity in propionyl and succinyl groups, originating from [1-14C]propionate, attained maximum values and then gradually decreased in both. Incorporation of [1-14C]isobutyrate proceeded slowly but reached a plateau and remained constant. While n-butyrate is not a normal constituent of methyl-glucose-containing lipopolysaccharides, it was incorporated as such when n-[1-14C]-butyrate was supplied in the medium. 4. [1-14C]Acetyl groups were readily displaced by unlabelled acetate. On the other hand, the specific radioactivity of the succinyl group continued to increase during a 3h incubation with unlabelled succinate. Propionyl and succinyl groups, labelled by [1-14C]propionate, were displaced slowly by unlabelled propionate or succcinate. The isobutyryl group of the lipopolysaccharides did not turn over, in contrast to the results obtained with the other acyl substituents.

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