Effect of lithium of responsiveness of rat uterine smooth muscle to angiotensin.
Studies were carried out to investigate the effect of Na+ deprivation on the response of rat uterine smooth muscle to angiotensin II (AII). Replacement of Na+ with Li+ in a low-Ca2+-, Mg2+-free solution resulted in a concentration-dependent inhibition of both AII and acetylcholine (ACh)-induced contractions. Inhibition was noted at 10% Li+ substitution and was usually complete when 50% of the Na+ was replaced by Li+. The inhibition was not observed when an equivalent amount of tris(hyroxymethyl)aminomethand (Tris+) or sucrose was used to replace Na+. However, elevation of Ca2+ concentration from 0.2 to 0.5 mM did prevent full expression of the Li+ inhibition of AII. The Li+ effect was rapid in onset (60% inhibition after 5 min preincubation) and readily reversible following removal of the Li+. If, however, the tissue was placed in a depolarizing solution (151 mM KCL), Li+ inhibition of AII WAS NO LONGER OBSERVED. These results are interpreted to mean that Li+ interferes with an essential Ca2+-dependent step involved in membrane excitation following agonist-receptor interaction. The results are discussed in relation to a previously suggested model for AII-induced contractions in this tissue.
D000109:Acetylcholine / Q000378:metabolism; D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D008094:Lithium / Q000494:pharmacology*; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology; D009215:Myometrium / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism; D014599:Uterus / Q000187:drug effects*
D000804:Angiotensin II; D010042:Ouabain; D008094:Lithium; D012964:Sodium; D000109:Acetylcholine; D002118:Calcium