Department of Pharmacology, Medical College, Baroda

Transcription

1 EFFECT OF METABOLIC POISO S AND DIGOXIN 0 THE ADRENERGIC NEURONE BLOCKING ACTIO OF GUANETHIDINE SAROJA JAYKAR * AND O.D. GULATI Department f Pharmaclgy, Medical Cllege, Barda Summary: The adrenergic neurne blcking actin f guanethidine in islated rabbit ileum preparatin (Finkleman) was neither prevented nr reversed by either idacetate r dinitrphenl. Hwever idacetate and dinitrphenl tgether partia liy prevented but did nt reverse the neurne blcking actin f guanethidine. Digxin ttally prevented but did nt reverse the neurne blcking actin f guanethidine. Key Wrds: Guanethidine Idacetate and dinitrphenl Adrenergic neurne blckade Digxin Gulati and Jaykar (7) studied the uptake f guanethidine indirectly by testing the ability f varius prcedures t prevent r reverse adrenergic neurne blckade in the periarterially stimulated islated rabbit ileum preparatin described by Finkleman (4). Theyshwed that adrenergic neurne blckade was prevented but nt reversed hy equilibratin withguanethidine at lw temperature (l0 C), in the absence f sdium r in the presence f tetrdtxin r nradrenaline. It was cncluded that the neurnal mechanism cncerned with the uptake f nradrenaline culd take up guanethidine and that this uptake f guanethidine wasenergy and sdium dependent. This paper reprts the effects f metablic inhibitrs and f digxin since it is knwn that digitalis glycsides inhibit the sdium-ptassium ATP-ase (12) METERJALS A D METHODS Details f the methd fr setting up Finkleman preparatin are described in the earlier paper(7). The relaxant respnses f the rabbit ileum t mesenteric nerve stimulatin shwed variatinsfrm preparatin t preparatin. Therefre, tw preparatins were set up simultaneusly. After eliciting cntrl respnses t different frequencies ne preparatin was treated withthe test drugs fr a specific perid f time. Bth the preparatins were nw expsed t guanethidine (3.3 x 10_ 6 M) fr 10 min. The preparatins were washed several times with Me- Ewan'sslutin (the slutin used fr bathing) and the respnses t nerve stimulatin were recrded. The effects f the test drug n respnses t nerve stimulatin were studied by setting upa third preparatin frm the same ileum and expsing it t the test drug fr a specified time. Guanethidine (3.8 x 10-6 M) prduced substantial t cmplete blck f respnses f the ileum t periarterial sympathetic nerve stimulatin at frequencies ranging frm 2 sec t 60 sec. Respnses / Presentaddress: 3245, East Jaffersn Avenue, Detrit, Michigan, U.S.A.

2 76 Jaykar and Gulati January I' Ind. J. Physil. Phar t nradrenaline (0.59 x lo-8_0.59 x 10-7M) were unaffected. The blcking actin lasted ~ mre than 3 hr. RESULTS Idacetate: Expsure f the tissue t idacetate (2.7 x 1O-6M) fr 30 min reducedi tne and pendular mvements which did nt recver cmpletely even after several washes ~ ver 2 hr. Respnses t nerve stimulatin were partially blcked (Fig. 1). Respnses t nrs drenaline (0.59 x x lo-7m) were nt blcked. In cntrl preparatins guanethidine prduced cmplete adrenergic neurne blckade all the frequencies. Idacetate (2.7 x 10-6M) kept in the bath fr 20 min befre expsing t tissue t guanethidine did nt prevent adrenergic neurne blckade due t guanethidine (Fig.! In tw experiments expsure f the preparatin t idacetate (2.7 x 10-6M) fr 30 min aft guanethidine had cmpletely blcked respnses t nerve stimulatin, did. nt reverse the adre. nergic neurne blcking actin f guanethidine. Dinitrphenl: Expsure f preparatins t dinitrphenl (0.5 x lo-3m) fr 30 ril reduced the tne and ablished.the pendular mvements. Respnses t nerve stimulati were ablished. Respnses t exgenus nradrenaline (0.59 x x lo-7m) were n affected. Sn after a few washes, the tne and the pendular mvements and respnses t nerve timulatin were restred t nrmal (Fig. 1). 10. "'? ~ 10 z 0 ~ '--' Z s ẋȯr r! r± r- 20 C0 CV CV CV i I, i I j 2 i 5"0'20' i i i i j j I I I 2' 5'10'20' ~ 102'0 I I I I! I CONTROL GUA IDA loa + GUA ONP ONP+ GUA loa + QNP Fig. I: R'!'pJ:lD f Finklernan preparatin t periarterial nerve stimulatin at different frequencies, e pressed as % f cntrls. Frm left t right the first panel shws cntrl and secnd, third, fifth seventh panels shw respnses after expsure f the preparatins t guanethidine (3.3xlO-G M) fr 10 idacetate (2.7xlO-G M) fr 30 min, dinitrphenl (0.5xlO-3 M) fr 30 min and idacetate (2.7xlO... and dinitrphenl (0.5xlO- 3 M) fr 30 min respectively. Respnses shwn in the furth, sixth and ei, panels were btained by expsing the preparatins t idacetate (2.7xlO-6 M) fr 20 min, dinitrph (0.5xlO- 3 M) fr 20 min and idacetate (2.7x10-8 M) and dinitrphenl (0.5xlO-3 M) fr 20 min pectively fllwed by further expsure t guanethidine (3.3.xlO-s M) fr 10 - min. Vertical lines indi standard errrs. Encircled figures abve each panel indicate the number f bservatins.

3 Adrenergic Neurne Blcking Actin f Guanethidine 77 In cntrl preparatins guanethidine ttally blcked respnses t nerve stimulatin at allthe frequencies: Expsure f the preparatin t dinitrphenl (0.5 x IQ-3M) fr 20 min befreadding guanethidine failed t prevent the adrenergic neurne blcking actin f guanethidine(fig. 1). Dinitrphenl (0.5 x IO-3M) kept fr 30 min in the bath failed t reverse the adrenergic neurne blcking actin f guanethidine (2 experiments). Idecetate and dinitrphenl: When the prepatatins were expsed t dicacetate. (2.7 x ID-GM) and dinitrphenl (0.5 x 10-3M) fr 20 min they were relaxed, the pendular mvementswere ablished and respnses t nerve stimulatin were ttally blcked (Fig. 1). Respnsest exgenus nradrenaline (0.59 x IQ x IQ-7M) were nt affected. After several washes the tne and pendular mvements were nly partially restred, but respnses t nervestimulatin cntinued t remain blcked fr ver 2 hr. In cntrl preparatins guanethidine prduced ttal adrenergic neurne blckade. Icdacetate (2.7 x IQ-6M) and dinitrphenl (0.5 x IO-3M) placed in the bath fr 20 min befre expsing the tissue t guanethidine partially prevented the adrenergic neurne blcking actin fguanethidine (Fig. 1). Cmbined treatment with idacetate (2.7 x IQ-GM) and dinitrphenl (6.5 x IQ-3M) fr 30 min failed t reverse the adrenergic neurne blcking actin f guanethidine (2 experiments). Digxin: Fig. 2 summarises the data. Fllwing expsure f the tissue t digxin (3.0 x IQ-GM) fr 20 min and washing, the tne and pendular mvements were reduced and respnses t nerve stimulatin were blcked. The actin f digxin lasted fr mre than 2 hr. Respnses t exgenus nradrenaline (0.59x IQ x IQ-7M) were nt affected. In cntrl preparatins guanethidine substantially blcked respnses t periarterial nerve stimulatin. In test preparatins digxin (3.0 x IO-GM) was placed in the bath fr 10 min fllwed by further expsure f the tissue t guanethidine. The adrenergic neurne blcking actin f guanethidine was ttally prevented. In the cntrl experiments described abve, where the tissue was expsed t guanethidineit was treated with digxin (3.0 x IQ-GM fr 212, min) after eliciting a panel f respnses t different frequencies f nerve stimulatin. The tissue was nw washed five t six times and the respnses t different frequencies were re-elicited. Respnses t nerve stimulatin were nt significantly (p > 0.05) different frm the cntrl guanethidine respnses. Thus digxin culd nt reverse the adrenergic blcking actin f guanethidine. DISCUSSION Interference with energy metablism reduces the uptake and retentin f nradrenaline in the islated tissues (3,6,13). The uptake f nradrenaline by the guinea pig islated left atrium

4 78 Jaykar and Gulati January 19 Ind, J. Physil. Pharm '4U :: f- Z u... eo! '-" 10~ ~rt Z ~ x ~... w Cl: 40 I I I I I I I J I J I 1 CONTROL GUA DIG DIG+ GUA GUA + OH? Fig. 2 : Respnses f Finkleman preparatins t periarterial nerve stimulatin at different frequencies, expres as % f cntrls. Frm left t right the first panel shws cntrl respnses; secnd and third panels sh' respnses after expsure f the preparatins t guanethidine (3.3xlD-6 M) fr 10 rnin and digxi (3.xlO-6 M) fr 20 min respectively; respnses shwn in the furth panel were btained after expsingi: preparatins t digxin (3.0xl0-6 M) fr 10 min fllwed by expsure t gunethidine (3.3.xl- 6 M) fr 11 min in the pressence f digxin and several wash-uts; after eliciting respnses shwn in the secnd pan the preparatins were treated with digxin (3.0xl0- G M) fr 20 min, washed and the respnses re-elicit (fifth panel). Vertical lines indicate standard errrs. Encircled figures abve each panel indicate t number.f bservatins. is nt exclusively dependent n carbhydrate metablism, and the energy required fr the uptake can als be prvided by aerbic xidatin f nncarbhydrate endgenus substrates (13). I1 the present study the metablic inhibitrs, idacetate r dinitrphenl individually did nt pre vent the adrenergic neurne blckade due t guanethidine but tgether were able t prevent ill partially. This agrees with the reprted metablic requirements fr the uptake f the nrade naline (13) and a- methyl-nradrenaline (8,9). The failure f idacetate and dinitrphenl t, cmpletely prevent the adrenergic neurne blcking actin f guanethidine may partly be duet. its passive diffusin int the adrenergic neurne. Alternatively the persistent adrenergic neur ne blcking actin f idacetate may have masked the preventing actin f metablic inhib~ 'tin n adrenergic neurne blckade by guanethidine. When idacetate and dinitrphen either separately r in cmbinatin were added t the bat h after expsure f the tissuet,

5 Vlume16 umber1 Adrenergic Neurne Blcking Actin f Guanethidine 79 guanethidine,the adrenergic neurne blcking actin f guanethidine was nt affected at all. It may,therefre, be justifiably cncluded that the uptake f guanethidine by the adrenergic neurneis in part energy-dependent. Digxin prevented the neurne blcking actin f guanethidine. Dengler et at (3) first demnstratedthat uabain culd blck the accumulatin f nradrenaline by brain and heart slices. Ouabain exerts this effect by inhibiting the transprt f nradrenaline acrss the cell membranerather than by acting n strage granules (1). Kirpekar and Wakade (10) shwed tbatcuabain can prduce marked interference with the uptake f nradrenaline by the perfused spleenf the cat. Ouabain blcks the transprt f 5-HT int platelets by an actin n the cell membrane(11). The amine transprt system is blcked indirectly thrugh the inhibitin f sdium-ptassium A TP-ase (12). An in-cupled transprt such as that described fr nradrenaline(2,5,10) and suggested fr guanethidine (7) finds further supprt frm the present data n tbepreventing actin f digxin f the adrenergic neurne blcking actin f guanethidine since thesdium-ptassium dependent ATP-ase which is crucial in determining extracellular sdium cncentratin is blcked by digitalis glycsides (12). It appears that sdium ins play an bligatryrle. ACKNOWLEDGEMENTS It is a pleasure t acknwledge the gifts f guanethidine by Ciba, Basle; f idacetate anddinitrphenl by Prf. C.V. Ramakrishnan, Department f Bichemistry, Faculty f Science, Barda; and f nradrenaline by Mr. A.V. Mdy f Unichem Labratries, Bmbay. This wrkwas supprted by a research grant frm the Cuncil f Scientific and Industrial Research, NewDelhi. REFERENCES I. Carissn, A.,.A. Hillarp and B. Waldeck. Analysis f the Mg.-ATP dependent strage mechanism in the amine granulla f the adrenal medulla. Acta Physil. Scand., 59, Suppl. 215 : 1-38, Crane, R.K. Prceedings f XV Annual Sympsium n Peptides f the Bilgical Fluids. ed. by Peeters, H. Amsterdam, Elsevier Publishing C., p , J. Dengler, H.J., LA. Micbaelsn, H.E. Spiegel and E.O. Titus. The uptake f labelled nrepinephrine by islated brain and ther tissues f the cat. Intern. J. Neurpharmac., 1: 23-38, Finkleman, B. On the nature f inhibitin in the intestine. J. Physil. (Lnd.), 70: , Gerrahan, F.J. and I.M. Glynn. The stichemetry f sdium pump. J. Physil. (Lnd.), 192 : , 1967_ 6. Green, R.D. and J.W. Miller. Evidence fr the active transprt f epinephrine and nrepinephrine by the uterus f the rat. J. Pharmac. Exp. Ther., 152 : 42-50, Gulati, O.D. and S. Jaykar. Factrs affecting the actin f guanethidine n adrenergic neurnes. Br. J. Pharmac., 42: , Harnberger, B. Reserpine-resistant uptake f catechlamines in islated tissues in the rat. Acta Physil. Seand., 71, Suppl. 295: 1-58, Ha.nberger, B. and T. Malmfrs. Uptake and Release f a-methyl-nradrenaline in vitr after reserpine pretreatment, histchemical study, Acta-Physil. Seand., 70 : , 1967.

6 80 Jaykar and Gulati 10. Kirpekar, S.M. and A.R. Wakade. Factrs influencing nradrenaline uptake by the perfused spleen the cat. J. Physil. (Land.)., 194: , PJetscher, A., W.P. Burkard, J.R. Tranger and K.F. Gey. Tw sites f 5-hydrxytryptamine uptake bld platelets. Life Sci. Oxfrd., 6: , Tissari, A.H., P.S. Schnhffer, D.F. Bgdanski and B.B. Brdie. Mechanism f bigenic amine transpr ll. Relatinship between sdium and mechanism f uabain. Blckade f the accumulatin f sert and nrepinephrine by synaptsemes. Ml. Pharmac., 5 : , Wakade, A.R. and R.F. Furchgtt, Metablic requirements fr the uptake and strage f nrepinep by the islated left atrium f the guinea pig. J. Pharmac. Exp. Ther., 163 : , 1968.