The distribution of six enzymes of oxidative metabolism along the rat nephron.

Abstract

Using quantitative methods, citrate synthase (CS), fumarase, fl-hydroxyacyl-coenzyme A (CoA) dehydrogenase (flOAC), 3-keto-acid CoA transferase (KCT), malic dehydrogenase (MDH), and malic enzyme were measured in seven defined parts of the nephron and in thin limb and papilla areas dissected from freeze-dried microtome seetions of rat kidney. The results not only show a wide range of activity along the nephron for each of the enzymes, but that the proportions between the enzymes vary markedly among the different parts of the nephron. This suggests the existence of major regional differences in the capacity to oxidize specific metabolites. The ratio between two citrate cycle enzymes, fumarase and CS, was 4-or 5-fold higher in proximal segments than in the gbomerulus or

An in-depth analysis of proteomics expression profiling in rat glomeruli utilizing LC-MS

“…The energy metabolism is closely related to hydrolysis or oxidation-reduction of proteins. Therefore, as compared with renal tubules, glomeruli need more hydrolases and oxidoreductases when involved in this process [43] (Figure 9). …”

Action of Aldosterone on Citrate Synthase in Cultured Renal Collecting Duct Cells

“…It functions as a source of metabolic fuel in the form of ATP [2,[25][26][27][28], Whithin the citric acid cycle, citrate synthase catalyzes and controls the important step of condensation of acetylCoA with oxaloacetate to citrate.…”

“…16.21] as well as on NaVK+-ATPase activ ity in the basolateral cell membrane [22,23,31,32], Enhancement ofN a+ reabsorption by these cells stimulated by a steroid hormone such as aldosterone has been found to be correlated with an increase in the activity of NaVK^-ATPase [12]. Enhanced ATPase ac tivity clearly requires an increased delivery of adenosine triphosphate (ATP) produced by mitochondrial enzymes involved in the citric acid cycle and in oxidative phosphorylation [9, 10, 13], Among these enzymes, citrate synthase seems to be a key enzyme which is able to accelerate the cycle [2,[25][26][27][28]33], The activity of the enzyme is decreased in rat and rabbit kidney after adrenalectomy [9,16]; aldosterone administration restores normal activity within 90 min [17,18], Spironolac tone blocks the effect of aldosterone on citrate synthase in this situation after adren alectomy. Although these results suggest that citrate synthase is an aldosterone-induced protein [11], this interpretation has been questioned by others, because in cell mono layer cultures from toad kidney and urinary bladder [6][7][8] aldosterone increases Na+ transport without any detectable change in citrate synthase activity.…”

Effect of Glucocorticoids on Mitochondrial Oxidative Enzyme and Na-K-ATPase Activities in the Rat Proximal Tubule and Thick Ascending Limb of Henle

“…The activity of Na-K-ATPase was measured in parallel. Citrate synthase, a key enzyme of the tricarboxylic acid cycle, reflects the distribution of mito chondria in the various renal epithelia [5]. 3-Ketoacid-CoA transferase (ketone bodies ox idation) and (3-hydroxyacyl-CoA dehydroge nase (fatty acid oxidation) were considered because ketone bodies and fatty acids are main energy substrates for both nephron seg ments [8].…”

“…Several features point to a particularly high mitochondrial energy production in the PCT and mTAL. including a high density of mitochondria per unit of cell volume [4]; the in vitro respiratory rates of these epithelia are far greater than those of other nephron segments [2], and the activities of mitochondrial oxidative enzymes are high er in the PCT and mTAL [5] than in other oxidative tissues with a high energy demand such as muscle fibers [6],…”