Effects of the beta-adrenergic agonist, ritodrine, and insulin on plasma potassium concentrations in fetal lambs.
Prolonged infusion of the beta 2-adrenergic agonist, ritodrine, into sheep during late pregnancy decreased maternal plasma K+ from 3.6 to 2.5 mmol l-1 during the first 6-8 h of infusion, as it does during tocolysis in women. This decrease was not accompanied by significant change in fetal plasma K+ concentration. Ritodrine infusion (1-3.5 micrograms kg-1 min-1) directly into the fetus also did not decrease fetal plasma K+ significantly. In contrast, insulin (2.5 mU kg-1 min-1), infused together with glucose (3.6 mg kg-1 min-1) directly into the fetus decreased fetal plasma K+ concentration by 0.8 mmol l-1 within 1 h. The results suggest immaturity in beta 2-adrenergic receptor regulation of electrogenic K+ uptake by muscle in fetal lambs.
University of Oxford, Growth and Development Unit, Wytham.
J M
JM
Bassett
J
J
Bomford
C
C
Hanson
J C
JC
Mott
C M
CM
Weeding
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D005260:Female; D005312:Fetal Blood; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D009994:Osmolar Concentration; D011188:Potassium / Q000097:blood*; D011247:Pregnancy; D012312:Ritodrine / Q000494:pharmacology*; D012756:Sheep / Q000196:embryology
D000318:Adrenergic beta-Agonists; D007328:Insulin; D012312:Ritodrine; D005947:Glucose; D011188:Potassium