Effects of Inorganic Anions on the Contractility of Vascular Smooth Muscle

Abstract

I<. 11. JHAMAYDAS Ah11 C'. $2'. h'hs.11.--Effects of iliorgnnic ,znions 011 the c.ontr,~ctility of vasci~lar snlooth mu~clc. Cali. j. E' hysioB. I'h,irinacol. 4.5, 67'5 (1 9t57).Contractile respon-es of i+ol,~tetf loops of rathit aorta tis51ics were first recorded in nornl,~I I<ret,s solutiorl and suf)secle~e~ltly in a inodifieci Krebs rnediltr~i ill nhich chloride ions were substituted with ecluivale~lt amoa~i~ts of one of the foreign anions, Br-, h03-', I-, SCN-, or S042--$Vith pot;lssi~~~n s1111atc or noradrenaline as the stirrlulatiiig agent, resporises of the tissrie.; cxposetl to these ailions for 1 minrate aild for 16 inini~tes were recorded. E'ot,lssinnr-induced contrac.tio~ls were potentiateel in the preseirce of J3r , NOS-, I-, and SCh-iorls t~u t were depressed in the presence of S0A2 ions. Iiespo~lses to ora adrenaline after 1-minute exposures were depressed in the presence of all the foreign aalioils whereas those induced after 16-nlinute exposures were pc>tenti,lted hy Br -riiid NOx-ions but were still depressed by T-. SCh , and SO< -ioiis. 7'he alterations in contractility produced by foreign ;~ilioiis have been attributed to their influence on the binding, release, aiirt reljinlding of c.;~lciu~ia ions. 'I'he differeilccs betm;een responses induced by K2S04 and ~ioradrenali~ie in the presence of foreign anlons cat1 be related to the utilization of calci~rl-ri from different binding sites in the cell mernf)rane.''This work was supported by the Life Insurance Medical 1:eiearch Furad and the Medical Research Coui~cil oi Canad,i."'1 his work represents plrtial fulfilment by I<. 11. Jham,end:is of tlac requirenlents for a postgr,~duate degree. -4 prelimill,nry report was presented a t the 1966 meeting od the I;ederrrtion of American Societies for Experilllerltdl I3iolr>gy, nnd nn abstract publislmed irn the 1;ederation

The effect of drugs on the constriction of isolated depolarized blood vessels in response to calcium or barium

“…Contraction of vascular smooth muscle in response to adrenaline seems to involve a different mechanism. The experiments of Hinke (1965), Jhamandas & Nash (1967) and Hudgins & Weiss (1968) indicate that during contraction in response to catecholamines the majority of the calcium ions which reach the contractile proteins come from a previously membrane-bound intracellular store. Barium ions may contract smooth muscle both by causing the contractile proteins to shorten directly and by releasing intracellular membrane-bound calcium (Daniel, 1964).…”

“…There is evidence that extracellular calcium ions enter the vascular smooth muscle cell in response to substances which produce contraction (Briggs, 1962;Waugh, 1962;Briggs & Shibata, 1966;Shibata & Carrier, 1967). In addition to the entry of extracellular calcium, the activity of some vasoactive drugs is best explained by the release of membrane-bound intracellular calcium in the vicinity of the contractile proteins (Hinke et al, 1964;Cuthbert & Sutter, 1965Jhamandas & Nash, 1967Hudgins & Weiss, 1968).…”

Evidence Against the Involvement of Prostaglandins in the Vasoconstrictor Action of Calcium Ion in Rat Mesenteric Blood Vessels

“…The mechanism by which PGE2 maintains or restores the response to noradrenaline in rat mesenteric blood vessels is not known but there are several potential sites of action in the sequence of excitationcontraction coupling. For example, noradrenaline produces vasoconstriction mainly by releasing intracellular Ca2+ from a binding site (Waugh, 1962; 0007-1188/81/10 0477-08 $01.00 Cuthbert & Sutter, 1965;Jhamandas & Nash, 1967;Hudgins & Weiss, 1968) to remove the inhibitory influence of the troponin C-like regulatory protein on the contractile proteins .…”