Life sciences · 2009
Modification of the effect of nifedipine in the pregnant rat myometrium: the influence of progesterone and terbutaline.
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Hajagos-Tóth Judit, Falkay George, Gáspár Róbert
Аннотация
AIMS: The aims of the study were to investigate the effects of nifedipine on potassium chloride (KCl)-evoked rat uterine contractions on different days of pregnancy in vitro, and the alterations in the effects of nifedipine on combination with terbutaline or progesterone.
MAIN METHODS: In rat myometrial rings taken on different days of pregnancy, rhythmic contractions were evoked with KCl in an isolated organ bath.
KEY FINDINGS: The relaxing effect of nifedipine was most expressed in the 25 mM KCl-induced uterine contractions, reaching the maximum on the last day of pregnancy (day 22). This effect was decreased by progesterone pretreatment in vivo. Synergism was observed in the uterus-relaxing effect of nifedipine+terbutaline, though the extent of potentiation depended on the sequence of administration of the two compounds. When terbutaline was added first in a single dose, the maximal inhibitory effect of nifedipine was lower. This decrease in the inhibition was suspended by a Ca(2+)-poor buffer, indicating the role of Ca(2+) channel activating effect of terbutaline.
SIGNIFICANCE: It is concluded that the uterus-relaxing effect of nifedipine is weakened by progesterone and may be enhanced by low concentrations of beta-mimetics. However, the administration of terbutaline cannot precede the administration of nifedipine.
MAIN METHODS: In rat myometrial rings taken on different days of pregnancy, rhythmic contractions were evoked with KCl in an isolated organ bath.
KEY FINDINGS: The relaxing effect of nifedipine was most expressed in the 25 mM KCl-induced uterine contractions, reaching the maximum on the last day of pregnancy (day 22). This effect was decreased by progesterone pretreatment in vivo. Synergism was observed in the uterus-relaxing effect of nifedipine+terbutaline, though the extent of potentiation depended on the sequence of administration of the two compounds. When terbutaline was added first in a single dose, the maximal inhibitory effect of nifedipine was lower. This decrease in the inhibition was suspended by a Ca(2+)-poor buffer, indicating the role of Ca(2+) channel activating effect of terbutaline.
SIGNIFICANCE: It is concluded that the uterus-relaxing effect of nifedipine is weakened by progesterone and may be enhanced by low concentrations of beta-mimetics. However, the administration of terbutaline cannot precede the administration of nifedipine.