Response to beta-blockers in maternal and fetal rat hearts in vitro.
The effects of beta-blockers on maternal and fetal heart rates have been assessed by comparing isoprenaline concentration-heart rate relationships of hearts isolated from pregnant rats. The normal and maximal heart rates obtained for the maternal and fetal hearts were similar to published data. A slightly but significantly higher concentration of isoprenaline was required to produce 50% of the maximal response of fetal hearts than maternal hearts, suggesting that fetal hearts were less sensitive to isoprenaline than the maternal hearts. The beta-blockers used (propranolol, labetalol, metoprolol and atenolol) all showed a lower affinity to the beta-receptors of fetal hearts than those of maternal hearts, as indicated by significant differences in the pA2 values. Given the similar effects of the beta-blockers in the maternal and fetal hearts it is concluded that pharmacokinetic considerations and beta-blocker selectivity should be used as the basis of choice when treating maternal hypertension during pregnancy.
Shen
J J
JJ
Department of Pharmacy, University of Otago Medical School, Dunedin, New Zealand.
Wanwimolruk
S
S
Mills
R G
RG
Roberts
M S
MS
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D007741:Labetalol / Q000494:pharmacology; D008790:Metoprolol / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D000319:Adrenergic beta-Antagonists; D001262:Atenolol; D011433:Propranolol; D008790:Metoprolol; D007545:Isoproterenol; D007741:Labetalol