Studies of the contracting mechanism induced by slow reacting substance of anaphylaxis (SRS-A): interaction with calcium.
The present study demonstrates the Ca2+ dependency of the contractions elicited by egg albumin and SRS-A in isolated tracheal preparations from sensitized guniea-pigs. The egg albumin contraction consisted of a rapid, initial and a long lasting, tonic phase; the first phase independent and the latter dependent of extracellular Ca2+. The SRS-A contraction was completely dependent of extracellular Ca2+ ions. On the other hand, the egg albumin contraction of the parenchymal strips was not influenced by extracellular Ca2+. SRS-A released Ca2+ from a microsomal fraction of sensitized lung tissue. This effect was, however, absent in microsomes from desensitized lung tissue. It is suggested that the Ca2+ -mobilizing effect of SRS-A is of utmost importance for the initiation of contraction of the tracheal smooth muscle.
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008168:Lung / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects*; D010047:Ovalbumin / Q000494:pharmacology; D013189:SRS-A / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects
D013189:SRS-A; D010047:Ovalbumin; D002118:Calcium