Effects of tyramine on the human uterine artery in vitro.
1. We have studied the effects of tyramine on the human uterine artery (HUA) in order to assess its site of action. 2. Tyramine (5 x 10(-5) to 10(-3) M) contracts the isolated human uterine artery. Tachyphylaxis appeared when concentration-response curves were repeated and the contraction was diminished by prazosin (10(-8), 10(-7) and 10(-6) M). The maximal contraction induced by tyramine (10(-3) M) was 25% of the maximal response to noradrenaline (10(-5) M). 3. After 2 hr of tyramine perfusion a decrease of the contractile response to KCl, 30 and 60 mM (15.0 and 12.9%) and noradrenaline 10(-6) M (83.2%) is shown. 4. However, when tyramine was previously added for 3 min to the bath, the response to KCl increased while the response to noradrenaline was lower. 5. A possible postsynaptic antagonistic effect for tyramine in the HUA is suggested in addition to its usual presynaptic effect.
Garcia de Boto
M J
MJ
Facultad de Medicina, Departamento de Medicina, Oviedo, Spain.
Molina
R
R
Andrés-Trelles
F
F
Hidalgo
A
A
D000818:Animals; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D013618:Tachyphylaxis / Q000502:physiology; D014439:Tyramine / Q000494:pharmacology*
D011189:Potassium Chloride; D009638:Norepinephrine; D014439:Tyramine; D011224:Prazosin