Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.13.12.5 (aequorin)
 1,451 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the effect of adenosine on cytoplasmic ionized calcium-force relationships in vascular smooth muscle (VSM) and determined the dose dependence of the observed effects. The bioluminescent protein aequorin was used as an index of cytoplasmic ionized calcium and was chemically loaded into ferret portal vein strips. The VSM strips were contracted with 33 mM potassium (K+), 5 X 10(-6) M phenylephrine (PE), or electrical stimulation. Force and aequorin light, i.e., cytoplasmic ionized calcium, were simultaneously recorded. Adenosine pretreatment (3.7 X 10(-6) M) reduced both force and light responses in contractures with K+, PE, or electrical stimulation. In contrast, the addition of adenosine during PE or K+ contractions decreased force without a change in light. Dose-response curves for the effects of adenosine on K+ contractures indicated that at low doses adenosine decreases force and cytoplasmic ionized calcium but that at high concentrations (greater than 3.7 X 10(-6) M) adenosine increases light and apparently relaxes VSM by desensitizing the myofilaments to cytoplasmic ionized calcium.
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PMID:Cellular Ca2+ monitored by aequorin in adenosine-mediated smooth muscle relaxation. 397 Jan 68

The effects of adenosine on Ca2+ transients and tension in ferret papillary muscles were investigated using the aequorin method. Adenosine (0.01-1 mM) reduced the peak of Ca2+ transients and caused a slight concentration-dependent decrease in tension. Adenosine prolonged the decay time of Ca2+ transients but did not alter the time course of tension. In isoproterenol (0.1 microM)-treated preparations, adenosine decreased the peak of Ca2+ transients but did not alter the peak of tension. Adenosine prolonged the isoproterenol-shortened decay time of Ca2+ transients. The effects of adenosine on Ca2+ transients were antagonized by the selective A1 receptor antagonist 8-cyclopentyl-1,3,-dipropylxanthine. In the presence of isoproterenol, adenosine (0.1 mM) shifted the intracellular [Ca2+]/tension relation to the left. These results can be explained by the hypothesis that adenosine inhibits the activity of adenylate cyclase via stimulation of the A1 receptor, other mechanisms however cannot be overlooked. The prolongation of the decay time of Ca2+ transients and the increase in the Ca2+ sensitivity of the contractile elements are the underlying mechanisms of adenosine which maintain developed tension in twitch response, although adenosine decreases the peak of Ca2+ transients.
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PMID:Effects of adenosine on Ca2+ transients and tension in aequorin-injected ferret papillary muscles. 781 58