Effects of PPADS and suramin on contractions and cytoplasmic Ca2+ changes evoked by AP4A, ATP and alpha, beta-methylene ATP in guinea-pig urinary bladder
| Autor: | Takeshi Katsuragi, Tatsuo Furukawa, Sadaharu Usune |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
medicine.medical_specialty
Cytoplasm Contraction (grammar) Nifedipine Suramin Urinary Bladder In Vitro Techniques chemistry.chemical_compound Adenosine Triphosphate Internal medicine medicine Channel blocker PPADS Pharmacology Chemistry Antagonist Calcium Channel Blockers Schild regression Endocrinology Pyridoxal Phosphate Calcium medicine.symptom Ap4A Dinucleoside Phosphates medicine.drug Muscle contraction Muscle Contraction Research Article |
| Zdroj: | British journal of pharmacology. 117(4) |
| ISSN: | 0007-1188 |
| Popis: | 1. The contraction and intracellular Ca2+ change evoked by diadenosine tetraphosphate (AP4A) were studied in the outer longitudinal muscle of the guinea-pig urinary bladder and compared with those evoked by ATP and alpha, beta-methylene ATP (a P2-purinoceptor agonist). 2. AP4A, ATP and alpha, beta-methylene ATP produced concentration-dependent transient contractions. These contractions were inhibited by PPADS (pyridoralphosphate-6-azophenyl- 2'-4'-disulphonic acid), 0.3- 30 microM, a P2x-purinoceptor antagonist, and suramin, 1-300 microM, a P2-purinoceptor antagonist in a concentration-dependent manner. From Schild plot analysis, the apparent pA2 values for PPADS for contractions evoked by AP4A, ATP and alpha, beta-methylene ATP were 6.86, 6.56, 6.74, and those for suramin were 6.01, 4.59 and 5.12, respectively; the Schild slopes for PPADS were 1.07, 1.14 and 1.06, and, those for suramin 0.75, 1.05 and 1.16, respectively. 3. AP4A (10 microM) and ATP (100 microM) failed to elicit any contraction of the tissue after a desensitization produced by repeated application of alpha, beta-methylene ATP (1 microM). 4. In fluorescence experiments with fura-2, the increases in [Ca2+]i and contraction evoked by AP4A were suppressed by suramin and nifedipine, an L-type Ca2+ channel blocker. 5. These findings suggest that P2x-purinoceptors, which are more sensitive to PPADS than suramin, exist on the outer longitudinal muscles of guinea-pig urinary bladder, and that the AP4A-evoked contraction results from Ca2+ influx. |
| Databáze: | OpenAIRE |
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