Roles of ERK and cPLA2 in the angiotensin II-mediated biphasic regulation of Na+-HCO3(-) transport. 2008

Yuehong Li, and Hideomi Yamada, and Yoshihiro Kita, and Motoei Kunimi, and Shoko Horita, and Masashi Suzuki, and Yoko Endo, and Takao Shimizu, and George Seki, and Toshiro Fujita
Department of Internal Medicine, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Regulation of renal proximal transport by angiotensin II (Ang II) is biphasic: low concentrations (picomolar to nanomolar) stimulate reabsorption, but higher concentrations (nanomolar to micromolar) inhibit reabsorption. Traditionally, the stimulatory effect has been attributed to activation of protein kinase C and/or a decrease in intracellular cAMP, whereas the inhibitory action has been attributed to the activation of phospholipase A2 (PLA2) and the subsequent release of arachidonic acid. The Ang II receptor subtype responsible for these effects and the intracellular signaling pathways involved are not completely understood. We isolated proximal tubules from wild-type, Ang II type 1A receptor (AT1A)-deficient, and group IVA cytosolic phospholipase A2 (cPLA2alpha)-deficient mice, and compared their responses to Ang II. In wild-type mice, we found that the stimulatory and inhibitory effects of Ang II on Na+-HCO3(-) cotransporter activity are both AT1-mediated but that ERK activation only plays a role in the former. The stimulatory effect of Ang II was also observed in AT1A-deficient mice, suggesting that this occurs through AT1B. In contrast, the inhibitory effects of Ang II appeared to be mediated by cPLA2alpha activation because high-concentration Ang II stimulated Na+-HCO3(-) cotransporter activity when cPLA2alpha activity was abrogated by pharmacological means or genetic knockout. Consistent with this observation, we found that activation of the cPLA2alpha/P450 pathway suppressed ERK activation. We conclude that Ang II activates ERK and cPLA2alpha in a concentration-dependent manner via AT1, and that the balance between ERK and cPLA2alpha activities determines the ultimate response to Ang II in intact proximal tubules.

UI MeSH Term Description Entries
D007687 Kidney Tubules, Proximal The renal tubule portion that extends from the BOWMAN CAPSULE in the KIDNEY CORTEX into the KIDNEY MEDULLA. The proximal tubule consists of a convoluted proximal segment in the cortex, and a distal straight segment descending into the medulla where it forms the U-shaped LOOP OF HENLE. Proximal Kidney Tubule,Proximal Renal Tubule,Kidney Tubule, Proximal,Proximal Kidney Tubules,Proximal Renal Tubules,Renal Tubule, Proximal,Renal Tubules, Proximal,Tubule, Proximal Kidney,Tubule, Proximal Renal,Tubules, Proximal Kidney,Tubules, Proximal Renal
D008297 Male Males
D008810 Mice, Inbred C57BL One of the first INBRED MOUSE STRAINS to be sequenced. This strain is commonly used as genetic background for transgenic mouse models. Refractory to many tumors, this strain is also preferred model for studying role of genetic variations in development of diseases. Mice, C57BL,Mouse, C57BL,Mouse, Inbred C57BL,C57BL Mice,C57BL Mice, Inbred,C57BL Mouse,C57BL Mouse, Inbred,Inbred C57BL Mice,Inbred C57BL Mouse
D008817 Mice, Mutant Strains Mice bearing mutant genes which are phenotypically expressed in the animals. Mouse, Mutant Strain,Mutant Mouse Strain,Mutant Strain of Mouse,Mutant Strains of Mice,Mice Mutant Strain,Mice Mutant Strains,Mouse Mutant Strain,Mouse Mutant Strains,Mouse Strain, Mutant,Mouse Strains, Mutant,Mutant Mouse Strains,Mutant Strain Mouse,Mutant Strains Mice,Strain Mouse, Mutant,Strain, Mutant Mouse,Strains Mice, Mutant,Strains, Mutant Mouse
D006706 Homeostasis The processes whereby the internal environment of an organism tends to remain balanced and stable. Autoregulation
D000804 Angiotensin II An octapeptide that is a potent but labile vasoconstrictor. It is produced from angiotensin I after the removal of two amino acids at the C-terminal by ANGIOTENSIN CONVERTING ENZYME. The amino acid in position 5 varies in different species. To block VASOCONSTRICTION and HYPERTENSION effect of angiotensin II, patients are often treated with ACE INHIBITORS or with ANGIOTENSIN II TYPE 1 RECEPTOR BLOCKERS. Angiotensin II, Ile(5)-,Angiotensin II, Val(5)-,5-L-Isoleucine Angiotensin II,ANG-(1-8)Octapeptide,Angiotensin II, Isoleucine(5)-,Angiotensin II, Valine(5)-,Angiotensin-(1-8) Octapeptide,Isoleucine(5)-Angiotensin,Isoleucyl(5)-Angiotensin II,Valyl(5)-Angiotensin II,5 L Isoleucine Angiotensin II,Angiotensin II, 5-L-Isoleucine
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D014662 Vasoconstrictor Agents Drugs used to cause constriction of the blood vessels. Vasoactive Agonist,Vasoactive Agonists,Vasoconstrictor,Vasoconstrictor Agent,Vasoconstrictor Drug,Vasopressor Agent,Vasopressor Agents,Vasoconstrictor Drugs,Vasoconstrictors,Agent, Vasoconstrictor,Agent, Vasopressor,Agents, Vasoconstrictor,Agents, Vasopressor,Agonist, Vasoactive,Agonists, Vasoactive,Drug, Vasoconstrictor,Drugs, Vasoconstrictor
D017693 Sodium Bicarbonate A white, crystalline powder that is commonly used as a pH buffering agent, an electrolyte replenisher, systemic alkalizer and in topical cleansing solutions. Baking Soda,Carbonic Acid Monosodium Salt,Sodium Hydrogen Carbonate,Bicarbonate, Sodium,Hydrogen Carbonate, Sodium,Soda, Baking
D044140 Receptor, Angiotensin, Type 1 An angiotensin receptor subtype that is expressed at high levels in a variety of adult tissues including the CARDIOVASCULAR SYSTEM, the KIDNEY, the ENDOCRINE SYSTEM and the NERVOUS SYSTEM. Activation of the type 1 angiotensin receptor causes VASOCONSTRICTION and sodium retention. Angiotensin II Type 1 Receptor,Angiotensin Type 1 Receptor,Angiotensin Type 1a Receptor,Angiotensin Type 1b Receptor,Receptor, Angiotensin, Type 1a,Receptor, Angiotensin, Type 1b,Angiotensin AT1 Receptor,Angiotensin AT1a Receptor,Angiotensin AT1b Receptor,Angiotensin II Type 1a Receptor,Angiotensin II Type 1b Receptor,Receptor, Angiotensin II Type 1,Receptor, Angiotensin II Type 1a,Receptor, Angiotensin II Type 1b,AT1 Receptor, Angiotensin,AT1a Receptor, Angiotensin,AT1b Receptor, Angiotensin,Receptor, Angiotensin AT1,Receptor, Angiotensin AT1a,Receptor, Angiotensin AT1b

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