Phosphoinositide 3-kinase mediates enhanced spontaneous and agonist-induced contraction in aorta of deoxycorticosterone acetate-salt hypertensive rats.
Arteries from deoxycorticosterone acetate (DOCA)-salt and N(omega)-nitro-L-arginine (L-NNA) hypertensive but not normotensive rats develop spontaneous tone. LY294002 and wortmannin, phosphoinositide 3-kinase (PI3-kinase) inhibitors, eliminate spontaneous tone. We hypothesized that PI3-kinase protein and/or activity was increased in hypertension and contributed to the observed enhanced contractility. PI3-kinase activity assays revealed 2-fold higher activity in thoracic aorta from DOCA-salt [systolic blood pressure (SBP)=184+/-5 mm Hg] compared with sham rats (SBP=111+/-2 mm Hg). Western analyses of aortic homogenates revealed the presence of p85alpha, p110alpha, p110beta, and p110delta but not p110gamma PI3-kinase subunits; p110delta protein was elevated in aorta of hypertensive rats as compared with sham. Aortic homogenates from L-NNA rats also had elevated p110beta protein density, but neither L-NNA nor DOCA-salt had differences in p85alpha and p110alpha. Total Akt density was unaltered, but pAkt was significantly lower in homogenates from DOCA-salt rats. LY294002 (20 micromol/L) and nifedipine (50 nmol/L) abolished Ca2+-induced spontaneous tone in aorta from DOCA-salt rats. However, LY294002 did not alter BayK8644-induced contraction, indicating that LY294002 does not inhibit L-type Ca2+ channels directly. PTEN (phosphatase and tensin homolog) and pPTEN were expressed but not different in aorta from DOCA-salt and sham rats. LY294002 corrected the enhanced contraction to KCl and norepinephrine in aorta from DOCA-salt rats. These data support an increase in PI3-kinase activity and p110delta density in aorta from L-NNA and DOCA-salt rats. Importantly, this increase contributes to the enhanced contractility observed in two models of hypertension.
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Mich 48824-1317, USA. taetscar@ msu.edu
Carrie A
CA
Northcott
Matthew N
MN
Poy
Sonia M
SM
Najjar
Stephanie W
SW
Watts
D000818:Animals; D001013:Aorta, Thoracic / Q000737:chemistry / Q000187:drug effects / Q000503:physiopathology*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003900:Desoxycorticosterone; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D019335:Nitroarginine; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000032:analysis / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D025521:Tumor Suppressor Proteins / Q000032:analysis / Q000096:biosynthesis; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002118:Calcium; D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D003900:Desoxycorticosterone; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D025521:Tumor Suppressor Proteins; D014662:Vasoconstrictor Agents; C494920:Akt1 protein, rat