Effects of L-norgestrel on the endothelium-dependent relaxation response of rabbit clitoral cavernous smooth muscles.
OBJECTIVE
To determine the effect of a popular oral contraceptive, L-norgestrel (a synthetic progestogen), on relaxing response of clitoral cavernous smooth muscles.


METHODS
Prospective, randomized study.


METHODS
Academic facility.


METHODS
Thirty adult female New Zealand White rabbits.


METHODS
We conducted isometric tension studies with norepinephrine, endothelium-dependent (acetylcholine) and endothelium-independent (sodium nitroprusside) vasodilators, and L-norgestrel. The effects of nonspecific nitric oxide synthase inhibitor (N(w)-nitro-L-arginine methyl ester) and the potassium channel blockers (1 and 10 mM tetraethylammonium as well as 10 microM glibenclamide) on the reactivities of clitoral cavernous strips were investigated.


METHODS
Causation and power of developed tension after treatment.


RESULTS
Acetylcholine, sodium nitroprusside, and L-norgestrel produced concentration-dependent relaxation of the norepinephrine-precontracted strips. Both endothelium removal and treatment with 10 microM N(w)-nitro-L-arginine methyl ester completely inhibited the relaxation response to acetylcholine and L-norgestrel, and supplementation with 10 mM L-arginine partially reversed the inhibition. Incubation with either tetraethylammonium (TEA) or glibenclamide reduced the L-norgestrel-induced relaxation in a dose-independent manner.


CONCLUSIONS
The L-norgestrel-induced relaxation of the clitoral cavernous smooth muscle is endothelium and nitric oxide dependent and may be related to more than two types of potassium channels activation.
Myung
Soon Chul
SC
Department of Urology, College of Medicine, Chung Ang University, Seoul, Korea.
Kim
Sae-Chul
SC
Lee
Shin Young
SY
Han
Ji Yup
JY
Lee
Moo Yeol
MY
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002987:Clitoris / Q000098:blood supply*; D003280:Contraceptives, Oral, Synthetic / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009644:Norgestrel / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011817:Rabbits; D019789:Tetraethylammonium / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
D003280:Contraceptives, Oral, Synthetic; D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D014665:Vasodilator Agents; D009599:Nitroprusside; D009644:Norgestrel; D019789:Tetraethylammonium; D001120:Arginine; D000109:Acetylcholine; D005905:Glyburide; D019331:NG-Nitroarginine Methyl Ester