Lymphocyte beta 2-adrenoceptors and adenosine 3':5'-cyclic monophosphate during and after normal pregnancy.
1. The beta 2-sympathomimetics, used to inhibit preterm labour, bind predominantly to beta 2-adrenoceptors, activating adenylate cyclase to form adenosine 3':5'-cyclic monophosphate (cyclic AMP), a messenger substance which inhibits the enzyme cascade triggering smooth muscle contraction. beta 2-Adrenoceptor density and cyclic AMP formation can be used as markers of beta 2-adrenergic effect. 2. The present study addresses the influence of pregnancy on the beta-adrenoceptor system. beta 2-Adrenoceptor density and cyclic AMP concentrations (basal and evoked by isoprenaline) in circulating lymphocytes were determined at three points in gestation (16, 29 and 37 weeks) and 9 weeks post partum in 22 normal pregnancies. (-)-[125Iodo]-cyanopindolol was used as the ligand to identify a homogeneous population of beta 2-adrenoceptors on lymphocytes. B- and T-cell fractions were estimated from the same samples. 3. beta 2-Adrenoceptor density decreased significantly during gestation until week 37 (P < 0.01), then increased post partum (P < 0.005). Cyclic AMP concentrations (basal and evoked by isoprenaline) were significantly lower after 16 weeks of gestation than post partum (P < 0.05). 4. The results, which cannot be explained in terms of a shift in the lymphocyte (B- and T-cell) ratio, indicate that beta-adrenoceptor density and function are reduced in normal pregnancy and only return to normal post partum. These findings may be of significance in devising future tocolytic therapy with beta 2-adrenoceptor agonists.
Department of Obstetrics, University of Zurich, Switzerland.
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von Mandach
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Gubler
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G
Engel
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Huch
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Huch
D000242:Cyclic AMP / Q000097:blood*; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007958:Leukocyte Count; D008214:Lymphocytes / Q000378:metabolism*; D049590:Postpartum Period; D011247:Pregnancy / Q000097:blood*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D012016:Reference Values
D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D007545:Isoproterenol