Contribution of Ras farnesyl transferase , MAP kinase and cytochrome P-450 metabolites to endothelin-1 induced hypertension

Endothelin  (ET-) is vasoactive peptide that acts via ET-A receptors coupling inducing vascular smooth muscle cell proliferation and contraction. ET- is involved in the development and maintenance of hypertension. Aim of this study was to determine the contribution of Ras farnesyl transferase, mitogen activated protein kinase (MAP kinase) and cytochrome P¬ (CYP) metabolites to ET- induced hypertension. ET- ( pmol/kg per minute) was chronically infused into to the jugular vein by use of mini-osmotic pump for  days in male Sprague-Dawley rats. Mean arterial blood pressure (MABP) in ET--treated rats was ± mm Hg (hypertensive rats) compared with ± mm Hg in control (normotensive) rats. Infusion of Ras farnesyl transferase inhibitor FPTIII ( ng/min), MAP kinase inhibitor PD- ( ng/min) and CYP inhibitor -ODYA ( ng/min) signifi cantly attenuated MABP to ±. mm Hg, ± mm Hg and ±. mm Hg, respectively. Th ese results suggest that CYP- metabolites and Ras/MAP kinase pathway contribute to the development of ET- induced hypertension. Further investigation has to be done to confi rm whether activation of RAS/MAP kinase pathway by arachidonic acid metabolites plays an important role in the development of ET- induced hypertension. ©  Association of Basic Medical Sciences of FBIH. All rights reserved


INTRODUCTION
There are three mature endothelin isoforms: ET-, ET- and ET-, of which the most potent isoform is endothelin- implicated in the physiological control of vascular smooth muscle cell (VSMC) and myocardial contractility [].ET- acts via ET-A receptors coupling inducing vascular smooth muscle cell contraction [].Endothelin-, a -amino acid peptide, is synthesized by the endothelium and it can induce proliferation of vascular smooth muscle cell and thus be implicated in pathogenesis of hypertension [-].ET- induces arachidonic acid release via activation of cytosolic phospholipase A (cPLA) [].Arachidonic acid is metabolized by cyclooxygenase into prostaglandins, by lipoxygenase into leukotrienes and by cytochrome P- into -, -, and -HETE [, ].It has been reported that Ras GTPase/MAP kinase pathway and cytochrome P- metabolites contribute to DOCA-Salt-induced hypertension and angiotension II-induced hypertension, as well [,].Aim of this study was to determine the contribution of Ras farnesyl transferase, mitogen activated protein kinase (MAP kinase) and cytochrome P¬ (CYP) metabolites to ET- induced hypertension.Since it has been reported that activation of Ras/MAP kinase pathway in angiotensin II-and norepinephrine-induced hypertension is mediated by arachidonic acid metabolites [, , ], we wanted to analyze whether is the same or similar mechanism in ET- induced hypertension.

Statistical analysis
Values are expressed as mean ± SEM.The data were analyzed by -way ANOVA, and difference between the means for multiple comparisons was determined by the Newman-Keuls test and a value difference of p<. was considered statistically significant.

DISCUSSION
It has been previously reported that Ras/MAP kinase pathway activation by CYP- metabolites contributes to the development of DOCA-Salt-induced hypertension [].Th e present study demonstrates that Ras/MAP kinase pathway activated probably by CYP- metabolites contributes to the development of ET- induced hypertension, as well.
Other vasoactive agents such as Norepinephrine (NE) and angiotensin II (ANG II) increase CaM kinase II and cPLA activities and thus release arachidonic acid [].The metabolites of arachidonic acid, such as

DECLARATION OF INTEREST
Authors report no confl ict of interest related to this study.
FARID LJUCA ET AL.: CONTRIBUTION OF RAS FARNESYL TRANSFERASE , MAP KINASE AND CYTOCHROME P450 METABOLITES TO ENDOTHELIN1 INDUCED HYPERTENSION inhibitor PD- ( ng/min) treated group, ) ET- plus CYP inhibitor -ODYA ( ng/min) treated group.Endothelin- was obtained from Amersham.Ras farnesyl transferase inhibitor FPTIII, MAP kinase inhibitor PD- and CYP inhibitor -ODYA were obtained from New England Biolabs.
of Health Guidelines for this kind of study.Animals were divided into: ) control group, ) ET- treated group ( pmol/ kg per minute), ) ET- plus Ras farnesyl transferase inhibitor FPTIII ( ng/min) treated group, ) ET- plus MAP kinase  BOSNIAN JOURNAL OF BASIC MEDICAL SCIENCES 2011; 11 (2): 85-86 Animals were anesthetized with sodium pentobarbital ( mg/kg), and left femoral artery was exposed surgically.A small incision was made in the femoral artery.And a catheter was inserted and connected to a pressure transducer (Grass model m, Grass Instruments) for blood pressure measurement.Blood pressure was recorded on a polygraph (model D; Grass polygraph).Mean arterial blood pressure (MABP) was expressed as mm Hg.
Eff ect of CYP-450 inhibitor 17-ODYA, COX inhibitor indometacin and LO inhibitor baicalein on MABP in ET-1 induced hypertensive rats FARID LJUCA ET AL.: CONTRIBUTION OF RAS FARNESYL TRANSFERASE , MAP KINASE AND CYTOCHROME P450 METABOLITES TO ENDOTHELIN1 INDUCED HYPERTENSIONcell proliferation through extracellular signal-regulated kinase activation mediated by cPLA[].ET- is involved in the development and maintenance of hypertension[, ].In our study, administration of ET- produced signifi cant rise in MABP compared with that in control (normotensive) rats.CONCLUSIONTh e present study demonstrates that Ras/MAP kinase pathway activated probably by CYP- metabolites contributes to the development of ET- induced hypertension.It seems to be common mechanism by which ET-, ANG II and NE induce hypertension.Further investigation has to be done to confirm whether activation of RAS/MAP kinase signal transduction pathway induced by different vasoactive agents by arachidonic acid metabolites is a universal mechanism in the development of hypertension.