Mechanisms of relaxation induced by prostaglandins in isolated canine uterine arteries.
OBJECTIVE
Prostaglandins liberated from the uterus in response to chemical and physical stimuli would be important modulators of uterine arterial tone and blood flow. This study was aimed at analyzing mechanisms of vasodilator action of prostaglandins in uterine arteries.


METHODS
Canine uterine artery strips were suspended in Ringer-Locke solutions for isometric tension recording.


RESULTS
Prostaglandin F2 alpha-induced relaxation was reversed to contraction by cyclooxygenase inhibitors and suppressed by tranylcypromine (prostaglandin I2 synthesis inhibitor) or diphloretin phosphate (an inhibitor of prostaglandin F2 alpha and prostaglandin I2 actions) but was unaffected by endothelium denudation. Prostaglandin E2-induced relaxation was not attenuated by indomethacin but was partially inhibited by a nitric oxide synthase inhibitor and endothelium denudation. Relaxation induced by beraprost (prostaglandin I2 analog) was suppressed by diphloretin phosphate but was not influenced by indomethacin and endothelium denudation.


CONCLUSIONS
It appears that prostaglandin F2 alpha-induced relaxation is mediated by prostaglandin I2 released from subendothelial tissues, whereas prostaglandin E2-induced relaxation is caused by release of endothelium-derived nitric oxide and also by an endothelium-independent mechanism.
Kimura
T
T
Department of Pharmacology, Shiga University of Medical Sciences, Ohtsu, Japan.
Yoshida
Y
Y
Toda
N
N
D000818:Animals; D001158:Arteries / Q000187:drug effects; D015237:Dinoprost / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D011464:Epoprostenol / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D011453:Prostaglandins / Q000494:pharmacology*; D014599:Uterus / Q000098:blood supply*; D014664:Vasodilation / Q000187:drug effects*
D011453:Prostaglandins; D009569:Nitric Oxide; C048081:beraprost; D015237:Dinoprost; D011464:Epoprostenol; D015232:Dinoprostone