Doxorubicin-induced changes in intracellular Ca2+ transients observed in cardiac myocytes isolated from guinea-pig heart

1994 ◽  
Vol 72 (6) ◽  
pp. 622-631 ◽  
Author(s):  
Jiahua Jiang ◽  
Kyosuke Temma ◽  
Tai Akera
Keyword(s):  
Guinea Pig ◽  
Electrical Field Stimulation ◽  
Electrical Field ◽  
Guinea Pig Heart ◽  
Fura 2 ◽  
Time To Peak ◽  
Doxorubicin Cardiotoxicity ◽  
Intracellular Ca ◽  
Induced Changes ◽  
Cellular Ca

Effects of doxorubicin on intracellular Ca2+ concentrations ([Ca2+]i) were examined using myocytes isolated from guinea-pig heart and loaded with fura 2. Changes in twitch contractions were assessed from the motion of myocytes. Ca2+ transients and contractions were triggered by electrical-field stimulation. Exposure of myocytes to doxorubicin depressed Ca2+ transients and contractions. The time to peak Ca2+ transient was prolonged, and Ca2+ sequestration was delayed. In myocytes treated with doxorubicin, an increase in external CaCl2 concentration from 1.2 to 3.6 mM increased the resting and peak [Ca2+]i and enhanced twitch contraction. In the presence of 3.6 mM CaCl2, isoproterenol failed to enhance Ca2+ transients or contractions of doxorubicin-treated myocytes. Effects of doxorubicin were compared with those of agents known to alter Ca2+ handling by myocytes. Caffeine enhanced the peak and resting [Ca2+]2 and contraction. Verapamil caused a rapid decrease in Ca2+ transients and twitch contractions. The effects of verapamil were reversed by isoproterenol in the presence of 3.6 mM CaCl2. Ryanodine alone and combined with doxorubicin depressed contractions and Ca2+ transients and elevated resting [Ca2+]i. Resting [Ca2+]i was further elevated by an increase in CaCl2 concentration and the addition of isoproterenol. The combination of verapamil and ryanodine inhibited Ca2+ transients and contractions. In the presence of verapamil and ryanodine, an increase in extracellular CaCl2 concentration increased resting and peak [Ca2+]i. Isoproterenol further elevated resting and peak [Ca2+]i and increased twitch contractions. These results indicate that doxorubicin alters cellular Ca2+ handling. The actions of doxorubicin are not mimicked by caffeine, verapamil, ryanodine, or the combination of verapamil and ryanodine. Among these agents, ryanodine produced effects that were closest to those observed with doxorubicin.Key words: doxorubicin cardiotoxicity, intracellular calcium, myocytes, ryanodine, verapamil, caffeine, isoproterenol, fura 2, guinea pig.

Acetylcholine release from canine isolated airway is not modulated by norepinephrine

1986 ◽  
Vol 61 (3) ◽  
pp. 1025-1030 ◽  
Author(s):  
J. G. Martin ◽  
B. Collier
Keyword(s):  
Guinea Pig ◽  
Acetylcholine Release ◽  
Electrical Field Stimulation ◽  
Output Pulse ◽  
Physiological Salt Solution ◽  
Guinea Pig Ileum ◽  
Cholinergic Nerves ◽  
Ach Release ◽  
Electrical Field ◽  
Neural Origin

We measured acetylcholine (ACh) release from canine isolated tracheal smooth muscle (TSM) and bronchial spirals using a radioenzymic assay technique. Tissue was incubated in physiological salt solution containing physostigmine (3.10(-5) M), atropine (10(-7) M), and choline (5.10(-6) M), and bath fluid was collected every 15 min for assay. There was a resting release of ACh of 209 +/- 44 pmol/g tissue (mean +/- SE) from 53 to 77 specimens of TSM. Electrical field stimulation (ES) increased ACh release, which was blocked by tetrodotoxin (10(-6) g/ml), confirming the neural origin of ACh. The ACh output during ES (2-ms pulses) at 10 Hz increased linearly from 188 +/- 50 pmol/g tissue (mean +/- SE) for a 1-min volley, to 323 +/- 57 for three volleys, and 544 +/- 128 for five volleys. The ACh output/pulse was constant during ES at 20, 15, 10, and 5 Hz, but it was significantly higher at 2 than at 5 Hz (P less than 0.005). Incubation of TSM with norepinephrine (NE, 10(-5) M) did not affect ACh output either at 2 or 10 Hz. Likewise, ACh output from bronchial spirals during ES and 2 Hz was unaffected by NE. In contrast, NE treatment of isolated guinea pig ileum reduced the ACh released by ES at 2 Hz to 40 +/- 7% (P less than 0.001) of the control ACh output. It is concluded that evoked release of ACh (output/pulse) from cholinergic nerves in canine airway is frequency dependent, as in guinea pig ileum, but that, unlike guinea pig ileum, NE does not modulate its release.

Effects of mucosal removal on guinea-pig airway smooth muscle responsiveness

1986 ◽  
Vol 70 (6) ◽  
pp. 571-575 ◽  
Author(s):  
Christopher Murlas
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Airway Smooth Muscle ◽  
Contractile Response ◽  
Electrical Field Stimulation ◽  
Physiological Salt Solution ◽  
Induced Responses ◽  
Field Stimulation ◽  
Electrical Field ◽  
Airway Mucosa

1. The contractile response to histamine, acetylcholine (ACh), KCl or electrical field stimulation (EFS) was examined in paired tracheal rings (one of each being denuded by mucosal rubbing), which were mounted in muscle chambers filled with a continuously aerated physiological salt solution at 37°C. 2. Removal of the respiratory mucosa increased the sensitivity of airway muscle to ACh, histamine and EFS, but not to KCl. The hypersensitivity of denuded rings to histamine and EFS was greater than to ACh. Atropine reduced the histamine hypersensitivity observed. 3. Pretreating intact preparations with indomethacin augmented their responsiveness to EFS, histamine and ACh. 4. Indomethacin augmentation of histamine- and EFS-induced responses was greater in preparations without epithelium. 5. We conclude that the airway mucosa may be associated with a factor that reduces airway smooth muscle responsiveness to stimulation.

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