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Evaluation of an epoxide (EET) as a hyperpolarizing factor mediating vasodilation to bradykinin (BK) but not acetylcholine (ACH)
ORALS:VasoactiveFactorsand VascularBiology
Evaluation OF AN EPOXtDE (EET) AS A HYPERPOLARtZfNG FACTOR MEDIATfNG VASODILATfON TO BRADYKININ (BK) BUT NOT ACETYLCHOLtNE {ACHY P. tiiey~l, J, C. McGiff,*D. Fulton. N;w Y;rk Medical Cbllege, Valhalla, N.Y. [n the rat isolatsd perfused hesrt and kidney treated 50#M)aodindometfracin (fND;2.8pfvf), With ttifrosrginine(NA; BK elicits vasodilation that is suswptibk to ii$ibitora of phOsphOjip~s, cytochroms P450 (CYP) ~d K . chammls,
imphcatmq a CYP-arachidmtatemetabohta acting us a hypcrpolsrtzing factor.‘firemostlikelycandidateis so EET. In the heq pharmacologicalcriteria wete used to determine whichof the EET ra ioisomerscouldpotentiallymediati the our EETs (lOpg) elicited vrrsodilatimr; effect of BK. All t$
5,6EET reduced perfusion pressure (PP) by 71*1lmmHg compared to less thnn 20mmHg for the other EETs (n=4-5). Nifedipirm (5nM), used as a probefor vas~dilatormechanisms dependenton closureof voltege-gatcdCa + channels,raduced responsesto BK (35+2vs 94+2mmHg; n=4-5) and 5,6EET (42+8 vs 71*1lmmHg) but nnt tbnse to the other EETs. Like BK: the res n~f to 5,6EET~aa reducedby charybdotoxin,an inhibitor oF Ca -activatedK channels(17+3vs 42+4mmHg; rr=4-5). These results are consistent with mediation by 5,6EET of BK-induced vamrtilation. However, a differeut mediator must be invoked for the renal vssodilator effect of Ach,which
also exhibits a substantialNO-independentcompnnantbut wbichis rroeffectedby inhibitoranf CYP at concentrations that
attenuate rosponws to BK. Nonetheless, the vasodilatoreffect of Ach in the kidney treated with NA and fND ntilizes a similar K+ channel as that nsed by BK in the kidney and heart. Thus, deoreases in PP of 6*3, 25+5 and 46f8mmHg tu 10, 30 and 100ng Ach, raspe.tively, were abolished by procsine (lmM) sod tetractbylmnmonium (lOmM) sod greatly attmmatod hy 1+1 and 3flmmHg, cbarybdotoxin (lOnM; n4),0, respectively, bnt not affected by iberiotoxin. These results indicate that a CYP mediator conwibutes to the reual actiotrsz~f BK but not to those of Acb although both stimulate Ca activated K’ channels.
Key Words:
Vasodilatirm, K+chsrmels, EETs, Hyperpokuizing factor
DEFECTIVE NITEGCOXIDE-PATHWAY 04 SALT-SENSITIVE ESSENTIAL HYPERTENSIVE PATIENTS. L. Ghiadoni, A. Virdis,S. Taddei*,J. Gonzales$, J. Salarar$,L. J. Andersen #, P. Dumnti, A. Salvetti*, 1ClinicaMedica, University ufPisa. Italy.$ Depsrtrrrent ofPhysiology, Univerx.ity of Mnrcia,Spain.#Psnnm Institute,Universityof Copsrdragen,Denmsrk, Essentialhypertensivepatients(EH) ars chsracterizedbyendothelial dysfunction.MoreoverEHc.malsobs characterizedbysodirrru-sensitivity whichcoudbe mediatedby a defectivenitric oxide(NO) pathway,Tbus in 5 salt-sensitive(SS) EH (accordingto the acute Grimm test), 5 saltresistmrt(SR) EH, while nn controlledNa+intske(urinaryNa+excretion 163+15 mEq/24tw), srrd 10 nonnotensivecontrols(NT) we studiedthe changesin foresnn blued flow (FBF; strain-gauge plethysnrugraphy) induced by intra-brachial infmion ofacetylcholine (ACH, 0.15, 0.45, 1.5, 4.5, 15 pg/100 ml/min), an endothelium-dependent vasodilator snd by sodium nitroprnsside (SNP, 1, 2, 4 pg/100 ml/min), m endothelirrnr-
independentvasodilator,SS EH showeda blomedvasndilation(VD) to ACH as comparsdto SR EH (increases in FBF: SS: 2.5+1,2, 25,5+6,9, 124.4*1 1.3,28-t.9i19.6,414 540.3+35.4*, 640.7+45.3;;
.3+37,1 ;SR:9.0+2.3,50.4+
.13,8,239,9+22,7,
p
●
essentialhypertension,salt sensitivity,endothelium,
AJH
1997;1O:2OA-21A
DAHL SALT-RESISTANT RAT BECOMES SALTSENSITIVE WITH INDUCIBLE NITRIC OXIDE SYNTHASE lNHD31TION.MARudd*, M Trolliet, S Hopa and J Lacelzo, BU Schoolof Medicitte,Boston, MA. Recent evidence has shown that induciblenitric oxide ,synthage(iNOS) induction leads to m inhibition of Na-KATPasein the proximaltobule, suggestinga role for iNOS in maintaining blood pressure by regulating plaama volume. Therefore, we hypothesized that Dabl sal-resiatsot (DR) animals will become hypertensive with selective iNOS irzhihitionduringincreasedardtintake. To test this hypothesis DRmrdDS ratsweregivett2-antizro-5,6-dihydro.6-methyl-4H. 1,3-thiazine(AMT), a novel speoificiohibitorof iNOS, for 5 dsyseztdtheoplacedon an 8% NaCl diet for 14 days DR and DS rats reeeiving NaCl alone ssrved as cootrols. Blood pressure (BP) was measuredby the tsil-cuffmethod, Slnin Bawd AMT(5oI@@ NoCI AM1’+ NaCl DR n
125f3
10
129~1 6
143f4 4
166i4““ 6
DS 138+2 201t4‘ 1565 “ 232~7“. n 12 9 3 3 *. ~ <0.05W. E)d. ●* =p <0,05 vsBassl srrdNaCl,ANOVAanafysis. while AMT skone or NaCl alone causedno sigtdtioatttchange
in BP io DR rats, AMT rmdNaCl used together iocreaaadBP by 37 rmuHg,AMT done cmmedso increesein baaetBP only in DS rats and enhuucedthe BP riaefollowingNaCl challenge iothese enirnsfs,Tbeaedatashowthat DR rets can becomesaksensitiveand that the hypertensionin DS cartbe exacerbated with iNOS inhibition. We conclude that iNOS plays a 8i$@cMtroleinthe developmerttof salt-inducedhypertension. KeyWorda: Nitric oxide, iNOS, hypertension,aelt
VONWILLEORAND FACTOR,TRANSCAPiLtARYALBUMINESCAPERATE, ANO FOREARMACETVLCNDLtNERESPONSIVENESS AS SURXERB OF, EN~TNEL~L ~VSFUNCTtON lNHVPERIENSIONANDATtiEFtDeCLERDSiS. Ft.PEDMNELLI G. OELL’OMO’, A. CORCHIA’,C. PRONTERA2, G.PENNO’, s. BANOINELLI;,M,NANNIPIERI’,R. NAVALESI$,I Clitrb Medica’,
MadicittsNuelaare’,II ClinicaMediea’,UniverWt#r di Piea,Italy BACKGROUSQ: Circtthtingvon WillebrandFactorIavals(vWF, a glyeoprofeinsecreted in graeter amounts by a dysfurrctionel enckrthelium), transeepillmyalbumineasapsrate (TAER,an ihrdex of rnecromolaculsrleakage across the andothelial Iayar of capiltarieaand arteries) and vaaorelaxationto intraarterial (i.a.) forearm infusion of acetyfcholine(Ach, a niirii oxide-releasing muacarinicagonist), are frequently used to study endotheliel function in both hypertension (Hf) and atherosclerosis (Ath). Howaver,how theaadisperateindicesrelate to aach other in the same aubject k unknown. SETMQQS:vWF Ievela (%, immtmoenzymetic method),TAER(Y!hr, the rate of iv. ‘=l-lebeled albuminddine over one hour)and the foraerm btoodftow (FBF, m~minxdl’,venousplethysmography)raapmse to i,a. Ach (7.5, 15and 30 p~min x6rnineach)wareevaluatadin j)8 controla(NOR, age:60i12, ASBPM,,+,:129+12 mmHg), 1)11 normotenaiveawith atheroaclerotk peripheral vascular diaeaae (PVD) (NOR-ATH, age:54+8,ASBPM,4+,:128N),ti)10 non atheroscleroticeasential hyprtensives (EM age:58t10, ASBPM,,+,:148+12)and jy)l 1 EH wilh atheroscleroticPVD (.s~-~m,age:SCH7,ASBPMU+;154*9). RESUUS:vWF waa 95i39 and 104*15 in NOR-ATH and EH-ATHvs _ 70+26and 67i29% in NoRarrdEH(Ath va rm-Ath:pc.005). TAER Waa11.1+3aIM 10,5+3in EH-ATHand EHVS9,2*3 and 8* I %Jhrin ATH and NOR respactivaly (Ht va no-Ht: p<.05). Maximum vaaorelexingresponseto Ach (FBF_jFBFW) was 4.8i2 and and EH-ATHvs 6.4+3,5 and 5.2+2.3 in ##o~and 5.9ti,2 in NOR-ATH EH (Ath vs no-Ath: p<.09; Ht vs no-Ht : p<.6). ~: Markerafor andothelialdysfunctionare not equivalent. vWF in aenatiiveto the atheroscleroticatatua,while TAER is rasponaive to BP Ievela,The forearmresponaeto i.a. Ach waa an only poor pradicforof At/randdid notdtierentiate ,Wat all in thinaeries. Kev Worda: VONWILLEaRANDFACTOR,TRANSCAPtLLARV ALattMIN ESCAPERATE, ACETVLCNOLINE, ENOOTNEUUM, ATHEROSCLEROSIS
Evaluation OF AN EPOXtDE (EET) AS A HYPERPOLARtZfNG FACTOR MEDIATfNG VASODILATfON TO BRADYKININ (BK) BUT NOT ACETYLCHOLtNE {ACHY P. tiiey~l, J, C. McGiff,*D. Fulton. N;w Y;rk Medical Cbllege, Valhalla, N.Y. [n the rat isolatsd perfused hesrt and kidney treated 50#M)aodindometfracin (fND;2.8pfvf), With ttifrosrginine(NA; BK elicits vasodilation that is suswptibk to ii$ibitora of phOsphOjip~s, cytochroms P450 (CYP) ~d K . chammls,
imphcatmq a CYP-arachidmtatemetabohta acting us a hypcrpolsrtzing factor.‘firemostlikelycandidateis so EET. In the heq pharmacologicalcriteria wete used to determine whichof the EET ra ioisomerscouldpotentiallymediati the our EETs (lOpg) elicited vrrsodilatimr; effect of BK. All t$
5,6EET reduced perfusion pressure (PP) by 71*1lmmHg compared to less thnn 20mmHg for the other EETs (n=4-5). Nifedipirm (5nM), used as a probefor vas~dilatormechanisms dependenton closureof voltege-gatcdCa + channels,raduced responsesto BK (35+2vs 94+2mmHg; n=4-5) and 5,6EET (42+8 vs 71*1lmmHg) but nnt tbnse to the other EETs. Like BK: the res n~f to 5,6EET~aa reducedby charybdotoxin,an inhibitor oF Ca -activatedK channels(17+3vs 42+4mmHg; rr=4-5). These results are consistent with mediation by 5,6EET of BK-induced vamrtilation. However, a differeut mediator must be invoked for the renal vssodilator effect of Ach,which
also exhibits a substantialNO-independentcompnnantbut wbichis rroeffectedby inhibitoranf CYP at concentrations that
attenuate rosponws to BK. Nonetheless, the vasodilatoreffect of Ach in the kidney treated with NA and fND ntilizes a similar K+ channel as that nsed by BK in the kidney and heart. Thus, deoreases in PP of 6*3, 25+5 and 46f8mmHg tu 10, 30 and 100ng Ach, raspe.tively, were abolished by procsine (lmM) sod tetractbylmnmonium (lOmM) sod greatly attmmatod hy 1+1 and 3flmmHg, cbarybdotoxin (lOnM; n4),0, respectively, bnt not affected by iberiotoxin. These results indicate that a CYP mediator conwibutes to the reual actiotrsz~f BK but not to those of Acb although both stimulate Ca activated K’ channels.
Key Words:
Vasodilatirm, K+chsrmels, EETs, Hyperpokuizing factor
DEFECTIVE NITEGCOXIDE-PATHWAY 04 SALT-SENSITIVE ESSENTIAL HYPERTENSIVE PATIENTS. L. Ghiadoni, A. Virdis,S. Taddei*,J. Gonzales$, J. Salarar$,L. J. Andersen #, P. Dumnti, A. Salvetti*, 1ClinicaMedica, University ufPisa. Italy.$ Depsrtrrrent ofPhysiology, Univerx.ity of Mnrcia,Spain.#Psnnm Institute,Universityof Copsrdragen,Denmsrk, Essentialhypertensivepatients(EH) ars chsracterizedbyendothelial dysfunction.MoreoverEHc.malsobs characterizedbysodirrru-sensitivity whichcoudbe mediatedby a defectivenitric oxide(NO) pathway,Tbus in 5 salt-sensitive(SS) EH (accordingto the acute Grimm test), 5 saltresistmrt(SR) EH, while nn controlledNa+intske(urinaryNa+excretion 163+15 mEq/24tw), srrd 10 nonnotensivecontrols(NT) we studiedthe changesin foresnn blued flow (FBF; strain-gauge plethysnrugraphy) induced by intra-brachial infmion ofacetylcholine (ACH, 0.15, 0.45, 1.5, 4.5, 15 pg/100 ml/min), an endothelium-dependent vasodilator snd by sodium nitroprnsside (SNP, 1, 2, 4 pg/100 ml/min), m endothelirrnr-
independentvasodilator,SS EH showeda blomedvasndilation(VD) to ACH as comparsdto SR EH (increases in FBF: SS: 2.5+1,2, 25,5+6,9, 124.4*1 1.3,28-t.9i19.6,414 540.3+35.4*, 640.7+45.3;;
.3+37,1 ;SR:9.0+2.3,50.4+
.13,8,239,9+22,7,
p
●
essentialhypertension,salt sensitivity,endothelium,
AJH
1997;1O:2OA-21A
DAHL SALT-RESISTANT RAT BECOMES SALTSENSITIVE WITH INDUCIBLE NITRIC OXIDE SYNTHASE lNHD31TION.MARudd*, M Trolliet, S Hopa and J Lacelzo, BU Schoolof Medicitte,Boston, MA. Recent evidence has shown that induciblenitric oxide ,synthage(iNOS) induction leads to m inhibition of Na-KATPasein the proximaltobule, suggestinga role for iNOS in maintaining blood pressure by regulating plaama volume. Therefore, we hypothesized that Dabl sal-resiatsot (DR) animals will become hypertensive with selective iNOS irzhihitionduringincreasedardtintake. To test this hypothesis DRmrdDS ratsweregivett2-antizro-5,6-dihydro.6-methyl-4H. 1,3-thiazine(AMT), a novel speoificiohibitorof iNOS, for 5 dsyseztdtheoplacedon an 8% NaCl diet for 14 days DR and DS rats reeeiving NaCl alone ssrved as cootrols. Blood pressure (BP) was measuredby the tsil-cuffmethod, Slnin Bawd AMT(5oI@@ NoCI AM1’+ NaCl DR n
125f3
10
129~1 6
143f4 4
166i4““ 6
DS 138+2 201t4‘ 1565 “ 232~7“. n 12 9 3 3 *. ~ <0.05W. E)d. ●* =p <0,05 vsBassl srrdNaCl,ANOVAanafysis. while AMT skone or NaCl alone causedno sigtdtioatttchange
in BP io DR rats, AMT rmdNaCl used together iocreaaadBP by 37 rmuHg,AMT done cmmedso increesein baaetBP only in DS rats and enhuucedthe BP riaefollowingNaCl challenge iothese enirnsfs,Tbeaedatashowthat DR rets can becomesaksensitiveand that the hypertensionin DS cartbe exacerbated with iNOS inhibition. We conclude that iNOS plays a 8i$@cMtroleinthe developmerttof salt-inducedhypertension. KeyWorda: Nitric oxide, iNOS, hypertension,aelt
VONWILLEORAND FACTOR,TRANSCAPiLtARYALBUMINESCAPERATE, ANO FOREARMACETVLCNDLtNERESPONSIVENESS AS SURXERB OF, EN~TNEL~L ~VSFUNCTtON lNHVPERIENSIONANDATtiEFtDeCLERDSiS. Ft.PEDMNELLI G. OELL’OMO’, A. CORCHIA’,C. PRONTERA2, G.PENNO’, s. BANOINELLI;,M,NANNIPIERI’,R. NAVALESI$,I Clitrb Medica’,
MadicittsNuelaare’,II ClinicaMediea’,UniverWt#r di Piea,Italy BACKGROUSQ: Circtthtingvon WillebrandFactorIavals(vWF, a glyeoprofeinsecreted in graeter amounts by a dysfurrctionel enckrthelium), transeepillmyalbumineasapsrate (TAER,an ihrdex of rnecromolaculsrleakage across the andothelial Iayar of capiltarieaand arteries) and vaaorelaxationto intraarterial (i.a.) forearm infusion of acetyfcholine(Ach, a niirii oxide-releasing muacarinicagonist), are frequently used to study endotheliel function in both hypertension (Hf) and atherosclerosis (Ath). Howaver,how theaadisperateindicesrelate to aach other in the same aubject k unknown. SETMQQS:vWF Ievela (%, immtmoenzymetic method),TAER(Y!hr, the rate of iv. ‘=l-lebeled albuminddine over one hour)and the foraerm btoodftow (FBF, m~minxdl’,venousplethysmography)raapmse to i,a. Ach (7.5, 15and 30 p~min x6rnineach)wareevaluatadin j)8 controla(NOR, age:60i12, ASBPM,,+,:129+12 mmHg), 1)11 normotenaiveawith atheroaclerotk peripheral vascular diaeaae (PVD) (NOR-ATH, age:54+8,ASBPM,4+,:128N),ti)10 non atheroscleroticeasential hyprtensives (EM age:58t10, ASBPM,,+,:148+12)and jy)l 1 EH wilh atheroscleroticPVD (.s~-~m,age:SCH7,ASBPMU+;154*9). RESUUS:vWF waa 95i39 and 104*15 in NOR-ATH and EH-ATHvs _ 70+26and 67i29% in NoRarrdEH(Ath va rm-Ath:pc.005). TAER Waa11.1+3aIM 10,5+3in EH-ATHand EHVS9,2*3 and 8* I %Jhrin ATH and NOR respactivaly (Ht va no-Ht: p<.05). Maximum vaaorelexingresponseto Ach (FBF_jFBFW) was 4.8i2 and and EH-ATHvs 6.4+3,5 and 5.2+2.3 in ##o~and 5.9ti,2 in NOR-ATH EH (Ath vs no-Ath: p<.09; Ht vs no-Ht : p<.6). ~: Markerafor andothelialdysfunctionare not equivalent. vWF in aenatiiveto the atheroscleroticatatua,while TAER is rasponaive to BP Ievela,The forearmresponaeto i.a. Ach waa an only poor pradicforof At/randdid notdtierentiate ,Wat all in thinaeries. Kev Worda: VONWILLEaRANDFACTOR,TRANSCAPtLLARV ALattMIN ESCAPERATE, ACETVLCNOLINE, ENOOTNEUUM, ATHEROSCLEROSIS