Effects of inorganic cations on K(+)-, 5-hydroxytryptamine- and noradrenaline-induced contractions of the isolated rat jugular vein and aorta.
We investigated the inhibitory effects of 1 mM of the inorganic cations, La3+, Cd2+, Mn2+, Ni2+ and Co2+ on contractions induced by K+ (100 mM) and 5-hydroxytryptamine (5-HT, 10(-5) M) in the isolated rat jugular vein and on contractions induced by K+ (100 mM), 5-HT (10(-5] and noradrenaline (NA, 10(-5) M) in the rat aorta. In the venous preparation, both K(+)- and 5-HT-induced Ca2+ influx could be suppressed completely by all cations studied. In the aorta, the K(+)-induced Ca2+ influx was antagonized completely only by Cd2+. The other cations were less effective and Mn2+ was completely ineffective. Similarly to that in the venous preparation, the 5-HT-induced Ca2+ influx in the aorta was abolished by all the cations. A similar picture was found for the NA-induced Ca2+ influx with the exception of Mn2+, which antagonized the NA-induced contractions only slightly. Although organic calcium entry blockers (CEBs) (nifedipine, diltiazem, flunarizine and gallopamil) inhibited NA-induced contractions to the same extent as did Mn2+, a combination of organic CEBs and Mn2+ abolished the NA-induced Ca2+ influx completely. Apparently, organic CEBs and Mn2+ block different components of the NA-induced Ca2+ influx pathway.
Gouw
M A
MA
Division of Pharmacotherapy, University of Amsterdam, Academic Medical Centre, The Netherlands.
Wilffert
B
B
Van Zwieten
P A
PA
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D002412:Cations / Q000494:pharmacology*; D066298:In Vitro Techniques; D007601:Jugular Veins / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology*
D002412:Cations; D012701:Serotonin; D009543:Nifedipine; D011188:Potassium; D009638:Norepinephrine