Nantenine blocks muscle contraction and Ca2+ transient induced by noradrenaline and K+ in rat vas deferens.
The effect of nantenine, an aporphine alkaloid isolated from Ocotea macrophylla H.B.K., was studied on contractions and Ca(2+) translocation induced by noradrenaline, Ca(2+), or K(+) in the isolated rat vas deferens from reserpinized animals. Concentration-response curves of calcium chloride (CaCl(2)) were performed in the vas deferens, in a Ca(2+)-free nutrient solution, using potassium chloride (KCl, 80 mM) as a depolarizing agent. In these conditions, nantenine (2.35 x 10(-4) and 4.7 x 10(-4) M) significantly reduced the maximum contractions (E(max)) of Ca(2+) (IC(50)=2.6 x 10(-4) M) and noradrenaline (IC(50)=2.9 x 10(-4) M). The contractile responses were totally recovered after the withdrawal of nantenine. In addition, experiments performed to measure simultaneously the contraction and the increase of intracellular Ca(2+) induced by noradrenaline (10(-5) M) or KCl (80 mM) showed that nantenine (2.35 x 10(-4) and 4.7 x 10(-4) M) significantly decreased both effects. The results suggest that a reversible block of Ca(2+) entry could be involved on the non-competitive-like antagonism of nantenine in rat vas deferens.
Ribeiro
Rosana de A
Rde A
Department of Pharmacology, Federal University of São Paulo, Rua Botucatu 862, 04023-062, São Paulo, Brazil. rosanari@terra.com.br
do Carmo
Lucia Garcez
LG
Vladimirova
Irina
I
Jurkiewicz
Neide H
NH
Jurkiewicz
Aron
A
D000818:Animals; D001060:Aporphines / Q000494:pharmacology*; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000502:physiology; D002122:Calcium Chloride / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D027444:Ocotea; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology*; D051381:Rats; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology
D001060:Aporphines; D010936:Plant Extracts; D011189:Potassium Chloride; D002122:Calcium Chloride; D002118:Calcium; D009638:Norepinephrine; C041615:nantenine