The intracellular calcium stores in the rabbit trachealis.
We investigated the role of the intracellular Ca2+ stores in the regulation of the rabbit tracheal smooth muscle contraction. Carbachol (10 microM)- and 80K-induced contractions were reduced by preincubating tissues in Ca2+-free (EGTA-PSS) solution. Contractile amplitude plotted as a function of the duration of EGTA-PSS preexposure was described by a biexponential for carbachol and a monoexponential for 80K. In EGTA-PSS, a prior caffeine (50 mM)-induced contraction prevented any subsequent phasic carbachol response; the converse was also true. In contrast, prior exposure to 80K increased the amplitude of a subsequent carbachol or caffeine contraction measured in EGTA-PSS. Repletion of Ca2+ plus either 80K or a low concentration of carbachol (0.3 microM) resulted in delayed tension development. Preincubation in forskolin (10(-5) M) in PSS also delayed tension development. We propose that the internal stores, most likely the sarcoplasmic reticulum in the airway muscle function both to supply and remove Ca2+ from the cytoplasm.
Nouailhetas
V L
VL
Department of Pharmacology, University of Miami School of Medicine, FL 33101.
Lodge
N J
NJ
Twort
C H
CH
Van Breemen
C
C
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D011817:Rabbits; D014132:Trachea / Q000187:drug effects / Q000502:physiology*
D005576:Colforsin; D002110:Caffeine; D004533:Egtazic Acid; D002217:Carbachol; D002118:Calcium