Torben Clausen

Effects of magnesium and terbutaline on contractility and K+ uptake in isolated human uterine muscle

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Mg++ (3 and 6 mmol/L), the beta 2-adrenergic agonist terbutaline (1 and 10 mumol/L), and dibutyryl cyclic adenosine 5'-monophosphate (0.1 and 1 mmol/L) suppressed spontaneous activity and the increase in contractile activity induced by ouabain or K(+)-free buffer in isolated human pregnant myometrium. The ouabain-suppressible rubidium 86 or potassium 42 uptake was unaffected by the presence of Mg++ (3 and 6 mmol/L), the beta 2-adrenergic agonist terbutaline (1 and 10 mumol/L), or dibutyryl cyclic adenosine 5'-monophosphate (1 mmol/L). However, loading of the strips with Na+ and incubation in high K+ induced a fivefold increase in rubidium 86 uptake. On the basis of these flux rates, our previous data on the total concentration of sodium-potassium pumps in the human myometrium, and an estimated maximum transport rate of the sodium-potassium pump of 8900 K+ ions per minute at 30 degrees C, it could be calculated that the sodium-potassium pump in the Na(+)-loaded strips reached around 80% of its maximal rate. Taken together, these results showed that the relaxant effects of Mg++, terbutaline, and dibutyryl cyclic adenosine 5'-monophosphate on human myometrium are not due to a stimulation of active sodium-potassium transport.
Original languageEnglish
JournalAmerican Journal of Obstetrics and Gynecology
Issue5 Pt 1
Pages (from-to)1543-51
Number of pages9
Publication statusPublished - 1991

    Research areas

  • Biological Transport, Bucladesine, Dose-Response Relationship, Drug, Female, Forskolin, Humans, Insulin, Magnesium, Myometrium, Potassium, Rubidium Radioisotopes, Sodium, Sodium-Potassium-Exchanging ATPase, Terbutaline, Time Factors, Uterine Contraction

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