Inhibition by tadalafil of contractility of isolated nonpregnant human myometrium.
OBJECTIVE
To investigate the inhibitory effect of tadalafil on the contractility of isolated nonpregnant human myometrium.


METHODS
The ability of tadalafil (25, 40, and 63 μM) to inhibit 55 mM KCl-induced contractility of isolated nonpregnant human myometrium was studied. The ability of the ATP-sensitive potassium channel blocker glibenclamide (10 μM) and the calcium-sensitive potassium channel (BKCa) blocker iberiotoxin (100 nM) to reverse the inhibitory effect of 40 μM tadalafil on 55 mM KCl-induced myometrial contractility was also studied.


RESULTS
Tadalafil produced a concentration-dependent inhibition of myometrial contractility that was statistically significant at 40 and 63 μM concentrations of tadalafil. The inhibition by tadalafil of myometrial contractility was statistically significantly reversed by the concurrent administration of glibenclamide and iberiotoxin.


CONCLUSIONS
These results suggest that tadalafil inhibits human myometrial contractility by opening ATP-sensitive potassium channels and BKCa channels. The opening of these channels could have been due to the action of raised intracellular levels of cGMP due to inhibition of PDE-5 by tadalafil. The results suggest that tadalafil could be investigated for use in clinical conditions requiring relaxation of the myometrium.
Department of Pharmacology and Clinical Pharmacology, Christian Medical College, Vellore, Tamil Nadu, India.
Sumalya
S
Sen
Division of Obstetrics and Gynaecology, Christian Medical College, Vellore, Tamil Nadu, India.
Anitha
A
Thomas
Department of Pharmacology and Clinical Pharmacology, Christian Medical College, Vellore, Tamil Nadu, India.
Saibal
S
Das
Department of Pharmacology and Clinical Pharmacology, Christian Medical College, Vellore, Tamil Nadu, India.
Jayanta Kumar
JK
Dey
Division of Obstetrics and Gynaecology, Christian Medical College, Vellore, Tamil Nadu, India.
Abraham
A
Peedicayil
Division of Obstetrics and Gynaecology, Christian Medical College, Vellore, Tamil Nadu, India.
Vinotha
V
Thomas
Department of Pharmacology and Clinical Pharmacology, Christian Medical College, Vellore, Tamil Nadu, India.
Jacob
J
Peedicayil
ATP-sensitive potassium channels; calcium-sensitive potassium channel channels; relaxant; uterus