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Acetylcholine and tachykinins involvement in the caffeine‐induced biphasic change in intracellular Ca 2+ in bovine airway smooth muscle
Author(s) -
Montaño Luis M,
Carbajal Verónica,
Arreola José L,
BarajasLópez Carlos,
FloresSoto Edgar,
Vargas Mario H
Publication year - 2003
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0705348
Subject(s) - caffeine , contraction (grammar) , tetrodotoxin , acetylcholine , muscle contraction , stimulation , chemistry , medicine , endocrinology , fura 2 , cytosol , biology , biochemistry , enzyme
Caffeine has been widely used as a pharmacological tool to evaluate Ca 2+ release from the sarcoplasmic reticulum in isolated smooth muscle cells. However, in nervous tissue this drug also causes neurotransmitters release, which might cause additional effects when smooth muscle strips are evaluated. To assess this last possibility, simultaneous measurements of contraction and cytosolic Ca 2+ concentration (using Fura–2/AM) were carried out in bovine airway smooth muscle strips during caffeine stimulation. A first stimulation (S1, n =11) with caffeine (10 m M ) induced a biphasic change in cytosolic Ca 2+ , which consisted of a transient Ca 2+ peak (254±40 n M , X ±SEM) followed by a plateau (92±13 n M ), and a transient contraction (204.72±31.56 mg tension mg tissue −1 ). A second caffeine stimulation (S2) produced a similar response but these parameters had a different magnitude. The S2/S1 ratios for these parameters were 0.69±0.02, 0.83±0.06 and 1.01±0.03, respectively. Addition of ω ‐conotoxin GVIA (1 μ M ) and tetrodotoxin (3.1 μ M ) before S2 significantly diminished these S2/S1 ratios (0.26±0.05, 0.26±0.09 and 0.64±0.11, respectively, n =5, P <0.05), implicating the neurotransmitters release involvement in the response to caffeine. A similar effect ( P <0.01) was observed with atropine (1 μ M , n =4), the fragment 4–11 of substance P (SP) (an SP receptor antagonist, 10 μ M , n =5), and with both substances ( n =4). We discarded a direct effect of ω ‐conotoxin GVIA (1 μ M ) plus tetrodotoxin (3.1 μ M ) or of atropine (1 μ M ) plus SP fragment 4–11 on smooth muscle cells because they did not modify caffeine responses in isolated tracheal myocytes. We confirmed by HPLC that caffeine increased the release of acetylcholine (from 0.43±0.19 to 2.07±0.56 n M mg tissue −1 , P <0.02) in bovine airway smooth muscle strips. Detection of substance P by ELISA was not statistically different after caffeine stimulation (geometric means before and after caffeine, 0.69 vs. 1.97 pg ml −1 mg tissue −1 , respectively, P =0.053). We concluded that acetylcholine and tachykinins release are involved in the caffeine‐induced biphasic changes in cytosolic Ca 2+ concentration.British Journal of Pharmacology (2003) 139 , 1203–1211. doi: 10.1038/sj.bjp.0705348