Plasma membrane proton ATPase from human kidney

Distal urinary acidification is thought to be mediated by a proton ATPase (H+-ATPase). We isolated a plasma membrane fraction from human kidney cortex and medulla which contained H+-ATPase activity. In both the cortex and medulla the plasma membrane fraction was enriched in alkaline phosphatase, maltase, Na+,K+-ATPase and devoid of mitochondrial and lysosomal contamination. In the presence of oligomycin (to inhibit mitochondrial ATPase) in the presence of ouabain (to inhibit Na+,K+-ATPase) and in the absence of Ca (to inhibit Ca2+-ATPase) this plasma membrane fraction showed ATPase activity which was sensitive to dicyclohexylcarbodiimide and N-ethylmaleimide. This ATPase activity was also inhibited by vanadate, 4,4'-diisothiocyano-2,2'-disulfonic stilbene and ZnSO4. In the presence of ATP, but not GTP or UTP, the plasma membrane fraction of both cortex and medulla was capable of quenching of acridine orange fluorescence, which could be dissipated by nigericin indicating acidification of the interior of the vesicles. The acidification was not affected by presence of oligomycin or ouabain indicating that it was not due to mitochondrial ATPase or Na+,K+-ATPase, respectively. Dicyclohexylcarbodiimide and N-ethylmaleimide completely abolished the acidification by this plasma membrane fraction. In the presence of valinomycin and an outward-directed K gradient, there was increased quenching of acridine orange, indicating that the H+-ATPase is electrogenic. Acidification was not altered by replacement of Na by K, but was critically dependent on the presence of chloride. In summary, the plasma membrane fraction of the human kidney cortex and medulla contains a H+-ATPase, which is similar to the H+-ATPase described in other species, and we postulate that this H+-ATPase may be involved in urinary acidification.     

Regional differences in ribonuclease content of rat and mouse kidney

Kidney cortex, red medulla and white medulla were separated into nuclei, mitochondria, microsomal and 105000g supernatant fractions. Assay of RNAase (ribonuclease) activity at pH7.8 revealed that, for each subcellular fraction, activity was much greater in cortex than in red or white medulla; this was true for both free RNAase and total (free plus latent) RNAase. For example, the free RNAase activity in the 105000g supernatant of cortex was 5 and 8 times higher than in red and white medulla respectively. No latent RNAase activity was found in any particulate fraction. Latent supernatant RNAase activities (suggesting presence of bound RNAase inhibitor) were similar in cortex and medulla. The cortex supernatant contained minimal free RNAase inhibitor, whereas that of the red and white medulla showed about one-third and one-tenth respectively of the inhibitor activity measured in liver. Adrenalectomy did not change RNAase activity in any fraction nor the content of free RNAase inhibitor in the kidney supernatant, but did decrease the liver RNAase inhibitor content by 40%. In supernatants from mouse kidney, both free and total RNAase activities of both cortex and red medulla were similar to those of rat red medulla. Mouse cortex contained appreciably higher amounts of free RNAase inhibitor than rat cortex. The difference between the rat and mouse cortical RNAase activity and inhibitor content may help explain the relative ease with which satisfactory renal polyribosome profiles were obtained from mouse kidneys. Our results, as well as those of Kline & Liberti [(1973) Biochem. Biophys. Res. Commun. 52, 1271–1277], showing that renal red and white medulla are more active than cortex in protein synthesis, are consistent with the hypothesis that the RNAase–RNAase-inhibitor system may participate in the regulation of protein synthesis.     

Demonstration of platelet activating factor receptor in guinea pig kidney.

Distribution of platelet activating factor (PAF) receptor was examined in the guinea pig kidney. Northern blot analysis showed a single band electrophoresed just below the 28S rRNA, and the mRNA was richest in the cortex with lesser amounts in the outer and then inner medulla. Scatchard analysis of membrane fraction using [3H]WEB 2086, a specific PAF receptor antagonist, revealed a single binding site with Bmax of 522, 228, 58 fmol/mg protein for the cortex, outer medulla and inner medulla, respectively. Kd values were in the same order of magnitude (10(-8) M). These results indicate the presence of a single class of PAF receptor in the guinea pig kidney which is most abundant in the cortex.     

Existence of acyl-CoA hydrolase-mediated pathway supplying arachidonic acid for prostaglandin synthesis in microsomes from rabbit kidney medulla.

We have previously shown that acyl-coenzyme A (CoA) hydrolase that hydrolyzes arachidonoyl-CoA (AA-CoA) to arachidonic acid (AA) and CoA is present in the cytosol of rabbit kidney medulla and that this enzyme can supply AA for prostaglandin (PG) synthesis in this region. In the present study, the existence of the acyl-CoA hydrolase-mediated pathway that supplies AA available for PG synthesis in microsomes from the kidney medulla was examined. AA-CoA (20 microM) was preincubated with the 105,000 g pellet (microsomes, 0.5 mg of protein) from the medulla for 5 min at 37 degrees C followed by incubation with the medulla microsomes (0.5 mg of protein) (the source of PG synthesizing enzymes) in the presence of hydroquinone and reduced glutathione for 5 min at 37 degrees C. The PGs formed were measured by high-pressure liquid chromatography using 9-anthryldiazomethane for derivatization. The addition of the microsomal fraction from the medulla in the preincubation mixture increased total PG formation from 3.86 to 8.70 nmol, and this stimulatory effect was somewhat weaker than that of the cytosolic fraction. On the other hand, the microsomal fraction in the kidney cortex has an extremely lower capacity to supply AA for PG synthesis than do medulla microsomes. These results suggest that, in kidney medulla, the microsomes as well as the cytosol have the potential route that supplies AA from AA-CoA for PG synthesis and that this pathway is mediated by acyl-CoA hydrolase.     

Properties and subcellular distribution of guanylate cyclase activity in rat renal medulla: correlation with tissue content of guanosine 3',5'-monophosphate.

The properties of the guanylate cyclase systems of outer and inner medulla of rat kidney were examined and compared with those of the renal cortex. A gradation in steady-state cyclic guanosine 3',5'-monophosphate (cGMP) levels was observed in incubated slices of these tissues (inner medula greater than outer medulla greater than cortex). This correlated with the proportion of total guanyl cyclase activity in the 100 000 g particulate fraction of each tissue, but was discordant with the relative activities of guanylate cyclase (highest in cortex) and of cGMP-phosphodiesterase (lowest in cortex) in whole tissue homogenates. Soluble guanylate cyclase of cortex and inner medulla exhibited typical Michaelis-Menten kinetics with an apparent Km for MnGTP of 0.11 mM, while the particulate enzyme from inner medulla exhibited apparent positive cooperative behavior and a decreased dependence on Mn2+. Thus, the particulate enzyme could play a key role in regulating cGMP levels inthe intact cell where Mn2+ concentrations are low. The soluble and particulate enzymes from inner medulla were further distinguished by their responses to several test agents. The soluble enzyme was activated by Ca2+, NaN3, NaNo2 and phenylhydrazine, whereas particulate activity was inhibited by Ca2+ and was unresponsive to the latter agents. In the presence of NaNo2, Mn2+ requirement of the soluble enzyme was reduced and equivalent to that of the particulate preparation. Moreover, relative responsiveness of the sollble enzyme to NaNO2 was potentiated when Mg2+ replaced Mn2+ as the sole divalent cation. These changes in metal requirements may be involved in the action of NaNO2 to increase cGMP in intact kidney. Soluble guanylate cyclase of cortex was clearly more responsive to stimulation by NaN3, Nano2, and phenylhydrazine that was soluble activity from either medullary tissue. The effectiveness of the agonists on soluble activity from outer and inner medulla cound also be distinguished. Accordingly, regulation and properties of soluble guanylate cyclase, as well as subcellular enzyme distribution, and distinct in the three regions of the kidney.     

Immunolocalization of betaine aldehyde dehydrogenase in porcine kidney.

Polyclonal anti-BADH serum was raised in rabbits against native BADH purified from porcine kidney. The antiserum cross-reacted strongly with BADH purified from kidney, Amaranthus palmierii, and Pseudomona aeuroginosa (1:1000), and weakly with Amaranthus hypochondriacus L (1:100). Antibodies bound to purified native kidney BADH in immunoblots showed a major band of an apparent molecular mass of 340 kDa and a subunit with an apparent molecular mass of 52 kDa. Data on activity assays showed higher activity in cortex sections (81.3 nmol/min/mg protein) than in medulla sections (21.3 nmol/min/mg protein). Immunolocalization of BADH in kidney tissue sections showed that BADH is found in cortex and medulla. In inner medulla, the enzyme was mainly localized in cells surrounding the tubules. Western blot analysis on extracts from the cortex and medulla sections showed higher concentration of BADH protein in cortex than in medulla. These results were in accordance with immunolocalization and activity analysis.     

应激引起血压升高大鼠血管升压素V1受体mRNA水平改变

实验在雄性ＳｐｒａｇｕｅＤａｗｌｅｙ 大鼠上进行。实验动物被随机分为对照组和应激组, 应激组大鼠每天给予电击足底结合噪声的应激刺激, 每日２ 次, 每次２ ｈ 。应激组大鼠在接受连续１５ ｄ 的慢性应激刺激后, 其尾动脉收缩压与对照动物相比有显著升高。对照组为１６－２５ ±０－６３ｋＰａ （ｎ ＝ ７） ; 应激组为１９－５５ ±１－４５ ｋＰａ （ｎ ＝ ８, Ｐ＜ ０－０５） 。用ＲＴＰＣＲ 结合Ｓｏｕｔｈｅｒｎ 印迹核酸分子杂交技术观察到, 血管升压素（ｖａｓｏｐｒｅｓｓｉｎ, ＡＶＰ）Ｖ１ 受体ｍＲＮＡ 广泛存在于大鼠下丘脑、皮质、延髓等部位以及心脏、肝脏、肾脏等组织中。用定量ＰＣＲ 方法观察到, 大鼠在接受慢性应激刺激之后, 其大脑顶叶皮质、下丘脑及延髓组织中ＡＶＰＶ１ 受体ｍＲＮＡ 水平均显著低于正常大鼠（ 顶叶皮质： Ｐ＜ ０－０５ ; 下丘脑： Ｐ＜ ０－０１ ; 延髓： Ｐ＜ ０－００１） , 而心脏、肝脏及肾脏组织中的ＡＶＰＶ１ 受体ｍＲＮＡ水平与正常大鼠相比均无明显差别（ 心脏： Ｐ＞ ０－０５ ; 肝脏： Ｐ＞ ０－０５ ; 肾脏：Ｐ＞ ０－０５） 。上述结果提示, 慢性应激刺激可引起大鼠不同部位脑组织ＡＶＰＶ１ 受体合成水平下调, 可能导致     

In vitro citrate synthesis by the dog kidney. Investigations with cortex, red and white medulla slices

In vitro utilization or production of citrate by the cortex, outer medulla or inner medulla of dog kidney was measured. Our data show: 1. An in vitro citrate synthesis or utilization capacity of the cortex greater than that of the red medulla. 2. An effect of pH on citrate synthesis or utilization capacity of the cortex, an effect not seen with medullary slices. 3. An absence of citrate synthesis or utilization by white medulla slices. It would seem that the citrate found in the white medulla and the papilla of the dog kidney in vivo was not produced in situ.     

Angiotensin converting enzyme predominates in the inner cortex and medulla of the rat kidney

Regional distribution of angiotensin converting enzyme(ACE) in the rat kidney was studied. The ACE activities in the inner cortex and outer medulla were about 10 and 5 times those in the outer cortex, respectively. The activity in the inner medulla or papilla was much the same as that in the outer cortex. Immunofluorescence was greatest in the proximal tubules in the inner cortex, while the outer medulla and the inner medulla or papilla showed a weak fluorescence. The brush border membranes isolated from the inner cortex also possessed about 10 times the ACE activity seen in the outer cortex. The results indicate that the major source of renal ACE is not the proximal convoluted tubules in the outer cortex, but rather the brush border membranes of proximal tubules in the inner cortex. The contribution of ACE in the inner cortex would therefore be predominant.     

Cyclooxygenase-1 and cyclooxygenase-2 expression in rat kidney and adrenal gland after stimulation with systemic lipopolysaccharide

Cyclooxygenase-2 (COX-2) is a recently discovered isoform of cyclooxygenase that is inducible by various types of inflammatory stimuli. Although this enzyme is considered to play a major role in inflammation processes by catalyzing the production of prostaglandins, the precise location, distribution, and regulation of prostaglandin synthesis remains unclear in several tissues. Using in situ hybridization histochemistry, we investigated the induction of COX-1 and COX-2 mRNA expression after systemic administration of a pyrogen, lipopolysaccharide (LPS), in kidney and adrenal gland in the rat. The COX-2 mRNA signals dramatically increased 1 h after LPS treatment in the kidney outer medulla and adrenal cortex, where almost no or little expression was observed in nontreated animals, and returned to control levels within 24 h. COX-2 mRNA levels increased in the kidney inner medulla 6 h after treatment. There was also a significant increase in mRNA levels in the kidney cortex and adrenal medulla. On the other hand, COX-1 mRNA levels did not show any detectable changes except in the kidney inner medulla, where a significant downregulation of mRNA expression was observed after LPS treatment. Light and electron immunocytochemistry using COX-2 antibodies showed that strong COX-2 immunoreactivity was localized to certain cortical cells of the thick ascending limb of Henle. In addition, based on double-staining with antiserum to nitric oxide synthase (NOS) four further cell populations could be identified in kidney cortex, including weakly COX-2-positive, NOS-positive macula densa cells. After LPS treatment, changes in COX-2 immunoreactivity could be observed in interstitial cells in the kidney medulla and in inner cortical cells in the adrenal gland. These results show that COX-2 is a highly induced enzyme that can be up-regulated in specific cell populations in kidney and adrenal gland in response to inflammation, leading to the elevated levels of prostaglandins seen during fever. In contrast COX-1 mRNA levels remained unchanged in this experimental situation, except for a decrease in kidney inner medulla.     

Blockade of AT1 receptors by losartan did not affect renin gene expression in kidney medulla

This study was designed to determine particular changes in the renin gene expression and activity in renal cortex and medulla after AT(1) receptor blockade. It was found that two-week-treatment with AT(1) blocker losartan induced an increase in tissue renin activity in both parts of kidney causing subsequent elevation of plasma renin activity. Renin mRNA in losartan-treated rats was increased only in cortex, suggesting cortex origin of elevated renin activity in medulla. Medullary renin mRNA indicated local synthesis of renin within the whole kidney and supported the idea of the presence of tissue renin-angiotensin system. Our results show that gene expression of renin in kidney medulla is insensitive to AT(1) receptor blockade and this points out that the regulation of kidney renin-angiotensin system probably differs from that in cortex.     

Copper accumulation in the soluble and particulate fractions of renal cortex in the streptozotocin-diabetic rat

The accumulation and subcellular distribution of copper in the kidney of streptozotocin-diabetic rats were investigated. Male Sprague-Dawley rats received streptozotocin (50 mg/kg body wt on two consecutive days) intraperitoneally and were fed either commercial or purified diet. The concentrations of copper, zinc, iron, and manganese present in intact kidney, renal cortex, and renal medulla were compared at various times. Chow-fed diabetic rats had a renal copper concentration 2.6 times greater than age-matched controls after 2 weeks. The concentration of zinc was only 30% higher in diabetic kidney than in control tissue, whereas the iron and manganese concentrations were similar for both groups. The additional complement of renal copper was localized entirely in the cortex and was significantly reduced by oral treatment with penicillamine, a copper chelating agent. When diabetic rats were fed purified diet (15-20 ppm Cu), the quantity of copper accumulated in the renal cortex increased from 2.3 to 8.7-fold higher than in control tissue from 1 to 4 weeks, respectively, after injection with streptozotocin. Copper levels in. both the soluble and particulate (165, 000g pellet) fractions of diabetic renal cortex were similarly increased at each time. Gel filtration Chromatographic analysis of the cytosol showed that all of the copper accumulated in the soluble fraction was associated with metallothionein. The distribution of excess copper in the particulate fraction was determined by differential centrifugation. The additional quantity of metal was localized in the crude nuclear fraction of renal cortex in the diabetic rat. Further analysis revealed that the lysosomal fraction from 3-weeek diabetic rats had a copper level 16-fold higher than in the controls. The possibility that accumulation of excessive levels of copper in the streptozotocin-diabetic kidney may contribute to the development of diabetic nephropathy is discussed.     

Effect of salt loading in the rat on adenylate cyclase and phosphodiesterase activity in kidney cortex, medulla and papilla.

Adenylate cyclase (AC) and phosphodiesterase (PDE) activities were studied in the cortex, medulla and papilla of the rat kidney. Sodium loading in vivo for 14 days resulted in a decrease of AC activity in the cortex, a small increase in the medulla and a substantial increase of AC activity in the papilla. Sodium loading caused reciprocal effects on PDE activity: an increase in kidney cortex and a decrease in kidney papilla. Loading of glucose in vivo or chronic administration of antidiuretic hormone in vivo did not cause the changes in AC or PDE observed after sodium loading. The possible significance of these findings is discussed.     

Alterations of renal cortex and medullary glycosaminoglycans in aging dog kidney

Age-related changes in renal function have been attributed to alterations in the chemical composition of the kidney tissues. Hence, the glycosaminoglycan composition of the renal cortex and medulla at varying age intervals was investigated. Glycosaminoglycans were isolated from the tissues by means of digestion with collagenase and pronase and purified by ethanol precipitation. Subsequent separation of various polyanions was accomplished by ion exchange chromatography on a Dowex 1-X2 column, using sodium chloride buffers of increasing ionic strengths. The glycosaminoglycans in each fraction were identified and quantitated by digestion with specific enzymes, including hyaluronidase, chondroitinase AC and ABC. The enzyme resistant material was separated and further digested with nitrous acid to quantitate the proportion of heparon sulfate. The results indicate that the glycosaminoglycan content of the renal medulla was much higher than the cortex at all the age intervals studied, and age-induced reduction was mainly cortical. There was a significant reduction in the heparan sulfate content of the cortex in aging. Interestingly, the major glycosaminoglycan content of the medulla was hyaluronic acid, which showed a sharp increase during aging, whereas heparan sulfate declined. Chondroitin sulfate was not altered due to age in either tissue. The molecular weight of hyaluronic acid was determined by column chromatography. Results indicate that the size of hyaluronate in the cortex was small and did not vary with age. In the medulla of the younger age group, a considerable amount of large size hyaluronate was observed. As age increased, the size decreased. The results strongly suggest that alteration in the renal glycosaminoglycans may be partly responsible for the age related protinuria and ionic imbalance.     

Location of renal ornithine decarboxylase activity

Renal ornithine decarboxylase (ODC) activity was found to be more prevalent in the medulla of the normal rat kidney than in the cortex. When renal ODC activity was stimulated by ethanol, growth hormone, ACTH, or corticosterone, proportional increases were observed in both medulla and cortex. After hypophysectomy, ODC activities fell equally in both areas of the kidney. The administration of cycloheximide, which is known to cause a rebound increase after six hours in overall renal ODC activity, was followed by an increase of medullary ODC activity while cortical activity remained suppressed.     

The nonuniformity of antibody distribution in the kidney and its influence on dosimetry

The therapeutic efficacy of radiolabeled antibody fragments can be limited by nephrotoxicity, particularly when the kidney is the major route of extraction from the circulation. Conventional dose estimates in kidney assume uniform dose deposition, but we have shown increased antibody localization in the cortex after glomerular filtration. The purpose of this study was to measure the radioactivity in cortex relative to medulla for a range of antibodies and to assess the validity of the assumption of uniformity of dose deposition in the whole kidney and in the cortex for these antibodies with a range of radionuclides. Storage phosphor plate technology (radioluminography) was used to acquire images of the distributions of a range of antibodies of various sizes, labeled with 125I, in kidney sections. This allowed the calculation of the antibody concentration in the cortex relative to the medulla. Beta-particle point dose kernels were then used to generate the dose-rate distributions from 14C, 131I, 186Re, 32P and 90Y. The correlation between the actual dose-rate distribution and the corresponding distribution calculated assuming uniform antibody distribution throughout the kidney was used to test the validity of estimating dose by assuming uniformity in the kidney and in the cortex. There was a strong inverse relationship between the ratio of the radioactivity in the cortex relative to that in the medulla and the antibody size. The nonuniformity of dose deposition was greatest with the smallest antibody fragments but became more uniform as the range of the emissions from the radionuclide increased. Furthermore, there was a strong correlation between the actual dose-rate distribution and the distribution when assuming a uniform source in the kidney for intact antibodies along with medium- to long-range radionuclides, but there was no correlation for small antibody fragments with any radioisotope or for short-range radionuclides with any antibody. However, when the cortex was separated from the whole kidney, the correlation between the actual dose-rate distribution and the assumed dose-rate distribution, if the source was uniform, increased significantly. During radioimmunotherapy, the extent of nonuniformity of dose deposition in the kidney depends on the properties of the antibody and radionuclide. For dosimetry estimates, the cortex should be taken as a separate source region when the radiopharmaceutical is small enough to be filtered by the glomerulus.     

Correlations of trace element levels within and between different normal autopsy tissues analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES)

Imbalance in trace metal metabolism may lead to metal interactions that may be of patho-physiological importance. Knowledge of the relation between trace metals in normal tissues is needed to assess abnormal deviations associated with disease. In this study correlations between Cu, Co, Cr, Fe, Mn, Ni, Se, Zn, Al, Ba, Cd, Pb and Sr within the same and between 6 different, normal autopsy tissues were determined using Spearman rank correlation analysis based on analytical data obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES). Fe-Co were correlated in most tissues. Cu-Mn, Zn-Cu, Zn-Mn and Zn-Cd were highly correlated in the kidney medulla. Ni-Ni, Sr-Sr and Cd-Cd were correlated between several tissues, while Fe-Fe, Zn-Zn and Cu-Cu were correlated between kidney cortex and medulla. Mn-Mn was highly correlated between the liver and brain front lobe, cerebellum and heart. High correlations were found for Ni-Co and for Se-Mn between the kidney cortex and brain front lobe and pancreas respectively. Inverse correlations were found for Se-Cd between kidney cortex and cerebellum, for Se-Cd and Cd-Zn between kidney medulla and heart, for Co-Sr and Fe-Sr between the liver and kidney cortex and heart respectively, and for Sr-Mn between kidney medulla and pancreas. A large number of trace elements are statistically correlated within and between different, normal tissues. Knowledge of these correlations may contribute to increase the understanding of kinetic interactions of trace metals in the body and the role of such interactions in normal and disturbed trace metal metabolism.     

Enzymes of fructose metabolism in human kidney.

Activities of enzymes involved in fructose metabolism were measured in samples of human kidney cortex and medulla. The enzymes are ketohexokinase, aldolase, NAD- and NADP-dependent alcohol dehydrogenase, aldehyde dehydrogenase, triokinase and glycerate kinase; hexose biphosphatase and sorbitol dehydrogenase were also investigated. With the exception of glycerate kinase, all enzymes involved in fructose metabolism were found in the human cortex and medulla. The enzyme levels in the medulla were low in comparison with the cortex.     

Hepatocyte nuclear factors as possible C-reactive protein transcriptional inducer in the liver and white adipose tissue of rats with experimental chronic renal failure

Little is known about the effects of coffee that are not related to the presence of caffeine. The aim of the study was to analyse changes in kidney function and nucleotide metabolism related to high intake of decaffeinated coffee. Mice consumed decaffeinated coffee extract for two weeks. Activities of AMP deaminase, ecto5′-nucleotidase, adenosine deaminase, purine nucleoside phosphorylase were measured in kidney cortex and medulla by analysis of conversion of substrates into products using HPLC. Concentration of nucleotides in kidney cortex, kidney medulla and serum were estimated by HPLC. Activity of ecto5′-nucleotidase increased from 0.032 ± 0.006 to 0.049 ± 0.014 nmol/mg tissue/min in kidney cortex of mice administered high-dose decaffeinated coffee (HDC) together with increase in cortex adenosine concentration and decrease in plasma creatinine concentration. HDC leads to increased activity of ecto5′-nucleotidase in kidney cortex that translates to increase in concentration of adenosine. Surprisingly this caused improved kidney excretion function.