Investigation of beta(2)-adrenoceptor subtype selectivity and organ specificity for bedoradrine (KUR-1246), a novel tocolytic beta-adrenergic receptor stimulant.
OBJECTIVE
The aim of this study was to evaluate the beta-adrenergic receptor (beta-AR) selectivity, organ specificity and efficacy of delaying the onset of spontaneous delivery of bedoradrine (KUR-1246), a novel uterine relaxant.


METHODS
beta-AR selectivity was evaluated in terms of the amount of cyclic adenosine monophosphate produced by bedoradrine, ritodrine and isoprenaline in Chinese hamster ovary cells expressing human beta(1)-, beta(2)-AR or beta(3)-AR. Inhibition of contractions of the atrium, trachea and proximal colon by bedoradrine were compared with those of the uterus in pregnant rats using an organ bath method. Finally, the delaying effect of bedoradrine on spontaneous labor was evaluated by an in vivo study using term pregnant rats.


RESULTS
EC(50) values of bedoradrine for cyclic adenosine monophosphate production in Chinese hamster ovary cells via beta(1)-, beta(2)- and beta(3)-AR were 2400 +/- 30, 2.9 +/- 0.10 and 363 +/- 3 nmol/L, respectively, indicating that bedoradrine had 832- and 126-fold higher selectivity for beta(2)-AR than for beta(1)- and beta(3)-AR. EC(50) values of bedoradrine for the uterus, atrium, trachea and proximal colon were 1.01 +/- 0.27, 2300 +/- 356, 1610 +/- 299 and 219 +/- 23.5 nmol/L, respectively. Thus, bedoradrine was 2280-, 1590- and 217-fold more specific for the uterus than for the atrium, trachea and proximal colon, respectively. Bedoradrine delayed the spontaneous delivery of 21-day-pregnant rats in a dose-dependent manner.


CONCLUSIONS
Bedoradrine is a promising drug for the treatment of preterm labor in obstetrical practice because it has better selectivity for beta(2)-AR and specificity for the uterus than currently used agents and may effectively delay spontaneous delivery.
Inoue
Yoshihito
Y
Department of Obstetrics and Gynecology, Faculty of Medicine, School of Medicine Fukuoka University, Jonan-ku, Fukuoka, Japan. zenjin@fukuoka-u.ac.jp
Yoshizato
Toshiyuki
T
Kawarabayashi
Tatsuhiko
T
D000081:Acetamides / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000096:biosynthesis; D004353:Drug Evaluation, Preclinical; D005260:Female; D009119:Muscle Contraction / Q000187:drug effects; D009281:Naphthalenes / Q000494:pharmacology* / Q000627:therapeutic use; D007752:Obstetric Labor, Premature / Q000188:drug therapy*; D009928:Organ Specificity; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects* / Q000502:physiology; D015149:Tocolytic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000187:drug effects*
D000081:Acetamides; D009281:Naphthalenes; D018343:Receptors, Adrenergic, beta-2; D015149:Tocolytic Agents; C425888:bedoradrine; D000242:Cyclic AMP