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Intracellular Signaling in the Regulation of Renal Na-K-Atpase. II

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Intracellular Signaling in the Regulation of Renal Na-K-Atpase. II Intracellular signaling in the regulation of renal Na-K-ATPase. II. Role of eicosanoids. T Satoh, … , H T Cohen, A I Katz J Clin Invest. 1993;91(2):409-415. https://doi.org/10.1172/JCI116215. Research Article We recently reported a novel intracellular mechanism of renal Na-K-ATPase regulation by agents that increase cell cAMP, which involves protein kinase A-phospholipase A2 and is mediated by one or more arachidonic acid metabolites (Satoh, T., H. T. Cohen, and A. I. Katz. 1992. J. Clin. Invest. 89:1496). The present studies were, therefore, designed to assess the role of eicosanoids in the modulation of Na-K-ATPase activity in the rat cortical collecting duct. The effect of various cAMP agonists (dopamine, fenoldopam, vasopressin, forskolin, and dibutyryl cAMP), which inhibited the pump to a similar extent (approximately 50%), was independent of altered Na entry as it was elicited in the presence of amiloride or nystatin, or when NaCl was replaced with choline Cl. This effect was completely blocked by SKF 525A or ethoxyresorufin, two inhibitors of the cytochrome P450-dependent monooxygenase pathway, or by pretreating the animals with CoCl2, which depletes cytochrome P450. Equimolar concentrations (10(-7) M) of the cyclooxygenase inhibitors indomethacin or meclofenamate caused only a partial inhibition of the cAMP agonists' effect on the pump, whereas nordihydroguaiaretic acid or A 63162, two inhibitors of the lipoxygenase pathway, were without effect. Furthermore, two products of this pathway, leukotriene B4 and leukotriene D4, had no effect on Na-K-ATPase activity, and ICI 198615, a leukotriene receptor antagonist, did not alter pump inhibition by cAMP agonists. Several […] Find the latest version: https://jci.me/116215/pdf Intracellular Signaling in the Regulation of Renal Na-K-ATPase II. Role of Eicosanoids Takeo Satoh, Herbert T. Cohen, and Adrian 1. Katz Department ofMedicine, University ofChicago Pritzker School ofMedicine, Chicago, Illinois, 60637 Abstract words: cortical collecting duct-cytochrome P450 monooxygen- ase * cyclooxygenase - lipoxygenase * leukotrienes We recently reported a novel intracellular mechanism of renal Na-K-ATPase regulation by agents that increase cell cAMP, Introduction which involves protein kinase A-phospholipase A2 and is me- diated by one or more arachidonic acid metabolites (Satoh, T., Na-K-ATPase, the biochemical equivalent of the Na:K pump, H. T. Cohen, and A. I. Katz. 1992. J. Clin. Invest. 89:1496). plays a central role in epithelial sodium transport. Dopamine The present studies were, therefore, designed to assess the role (DA),' a potent natriuretic hormone, decreases tubular sodium of eicosanoids in the modulation of Na-K-ATPase activity in reabsorption (1, 2), due in part to the inhibition of Na-K- the rat cortical collecting duct. The effect of various cAMP ATPase activity in the proximal convoluted tubule (3) and cor- agonists (dopamine, fenoldopam, vasopressin, forskolin, and tical collecting duct (CCD) (4). We recently reported that DA, dibutyryl cAMP), which inhibited the pump to a similar extent receptor activation increased cAMP accumulation in the CCD, (- 50%), was independent of altered Na entry as it was elicited and that dopamine and other agents that increase cell cAMP in in the presence of amiloride or nystatin, or when NaCl was this segment, such as vasopressin, forskolin, or exogenous replaced with choline Cl. This effect was completely blocked by cAMP, inhibited Na-K-ATPase activity in a quantitatively SKF 525A or ethoxyresorufin, two inhibitors of the cytochrome comparable manner. This novel mechanism of Na:K pump P450-dependent monooxygenase pathway, or by pretreating modulation involves activation ofprotein kinase A (PKA), and the animals with CoC12, which depletes cytochrome P450. subsequently of phospholipase A2 (PLA2) (5). Equimolar concentrations (10-' M) of the cyclooxygenase in- Arachidonic acid, which is released by PLA2 activation, hibitors indomethacin or meclofenamate caused only a partial is metabolized to bioactive eicosanoids through either the inhibition of the cAMP agonists' effect on the pump, whereas cyclooxygenase, cytochrome P450-dependent monooxygen- nordihydroguaiaretic acid or A 63162, two inhibitors of the ase, or the lipoxygenase pathways, one or more of which may lipoxygenase pathway, were without effect. Furthermore, two mediate cAMP-dependent pump inhibition in the kidney. products of this pathway, leukotriene B4 and leukotriene D4, PGE2, a cyclooxygenase product, inhibits renal Na-K-ATPase had no effect on Na-K-ATPase activity, and ICI 198615, a leu- activity (6, 7) and mediates the decrease in CCD sodium reab- kotriene receptor antagonist, did not alter pump inhibition by sorption produced by cAMP (8). In addition, 11,12-dihy- cAMP agonists. Several P450 monooxygenase arachidonic droxyeicosatrienoic acid (1 1, 12-DHT), generated via the cy- acid metabolites (5,6-epoxyeicosatrienoic acid; 11,12-epoxyei- tochrome P450-dependent monooxygenase pathway, also in- cosatrienoic acid; 11,12-dihydroxyeicosatrienoic acid; and hibits the renal Na:K pump, and its production is 12(R)-hydroxyeicosatetraenoic acid) as well as PGE2 inhibited cAMP-dependent (9). Other metabolites of this pathway, such the Na:K pump in dose-dependent manner, but the effect of as 5,6-epoxyeicosatrienoic acid (5,6-EET) (10) and 12(R)-hy- PGE2 was blocked when Na availability was altered, whereas droxyeicosatetraenoic acid [12(R)-HETE] (11), inhibit renal that of 12(R)-HETE remained unchanged. We conclude that Na-K-ATPase activity as well. In contrast, little is known about the cytochrome P450-monooxygenase pathway of the arachi- the effect of lipoxygenase products on the renal Na:K pump. donic acid cascade plays a major role in the modulation of Na:K Besides the uncertainty regarding the pathway of arachi- pump activity by eicosanoids in the rat cortical collecting donic acid metabolism involved, it is also unclear whether the duct, and that products of the cyclooxygenase pathway may action ofeicosanoids that mediate the cAMP-dependent inhibi- contribute to pump inhibition indirectly, by decreasing tion is on the pump itself or indirect; e.g., by altering luminal intracellular Na. (J. Clin. Invest. 1993. 91:409415.) Key Na entry. The purpose of this study was, therefore, to identify the arachidonic acid metabolic pathways involved in cAMP- dependent pump regulation in rat CCD and to elucidate the A portion of this work has been presented in part at the annual meeting mechanism(s) underlying this phenomenon. of the American Society for Clinical Investigation, Seattle, WA, on May 4, 1991, and has been published in abstract form (1991. Clin. Res. Methods 39:223.) Address correspondence and reprint requests to Adrian I. Katz, Microdissection. Kidneys were obtained from male Sprague-Dawley M.D., Department of Medicine, MC 5100, University of Chicago, rats weighing 200-300 g that had free access to regular laboratory chow 5841 S. Maryland Ave., Chicago, IL 60637. Receivedfor publication 1 April 1992 and in revisedform 20 July 1. Abbreviations used in this paper: AA, arachidonic acid; AVP, argi- 1992. nine vasopressin; CCD, cortical collecting duct; DA, dopamine; DHT, dihydroxyeicosatrienoic acid; EET, epoxyeicosatrienoic acid; HETE, J. Clin. Invest. hydroxyeicosatetraenoic acid; HPETE, hydroxyperoxyeicosatetraen- © The American Society for Clinical Investigation, Inc. oic acid; MTAL, medullary thick ascending limb; NDGA, nordihydro- 0021-9738/93/02/0409/07 $2.00 guaiaretic acid; PKA, protein kinase A; PLA2, phospholipase A2, SKF Volume 91, February 1993, 409-415 525A, 2-diethylaminoethyl 2,2-diphenylvalerate hydrochloride. NaK Pump Modulation by Eicosanoids in Rat Cortical Collecting Duct 409 and tap water. The procedure for tubule microdissection has been re- Dimethylsulfoxide was used as a solvent for forskolin, nystatin, ICI ported previously in detail (12). After anesthesia, the left kidney was 198615, and A63 162, whereas indomethacin, ethoxyresorufin, perfused in situ through a catheter placed in the left renal artery with NDGA, the leukotrienes, and the P450 monooxygenase products were cold collagenase solution, a modified HBSS containing (in mM) 137 dissolved in ethanol. Final concentrations of DMSO and ethanol dur- NaCl, 5 KCl, 0.8 MgCl2, 0.33 Na2HP04, 0.44 KH2PO4, 1 MgCl2, 10 ing incubations were < 0.1% and < 0.5%, respectively, and were shown Tris-HCl, 1 CaCl2 at pH 7.4 with 400 U/ml collagenase (type I; Sigma not to influence Na-K-ATPase activity in preliminary experiments us- Chemical Co., St. Louis, MO) and 0.05% BSA. The kidney was re- ing these solvents alone. moved and cut along the corticopapillary axis into pyramids, which Statistics. Statistical analysis was done with one-way analysis of were incubated in the same collagenase solution at 370C for 7 min. variance followed by the Bonferroni correction for multiple compari- After incubation, the pyramids were rinsed with cold modified HBSS sons. Results in text and figures are means±SE. (0.25 mM CaCl2), and CCD segments were dissected freehand in the same solution at 4VC under stereomicroscopic observation. Isolated Results CCD were individually transferred to a concave bacteriological slide and photographed to determine their length. of cAMP agonists on Na-K-A TPase activity To obtain tubules with patentlumina (for experiments using amilo- Effect ride or choline chloride), animals received by jugular vein infusion an Several experimental maneuvers that increase cAMP accumu- agarose solution (1 ml/100
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