DTIC ADA274875: Effects of Potassium Channel Blockers pdf

DTIC ADA274875: Effects of Potassium Channel Blockers

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The K+ channel openers cromakalim and pinacidil induced a concentration-dependent reduction in atrial contraction force with EC50 values of 25 +/- 2 and 37 +/- 2 micromol/l, respectively. This depressant effect was antagonised by 50 micromal/l tacrine which displaced the concentration-response curves of cromakalim and pinacidil to the right. The respective DR50 values were 3.8 and 2.3. Increasing the tacrine concentration (100 and 500 micromol/l) produced no additional effect on the concentration-response relationships. Addition of 1 micromol/l atropine enhanced the antagonism due to tacrine by increasing the DR50 value from 3.8 to 6.5 for cromakalim and from 2.3 to 5.2 for pinacidil. Glibenclamide, an ATP-sensitive K+ channel blocker, competitively inhibited the negative inotropic effects of cromakalim and pinacidil. The respective dissociation constants for glibenclamide against cromakalim and pinacidil were 0.57 and 0.35 Micromol/l. Neither apamin nor variation in external Ca2+ concentration affected the negative inotropic effects of the K+ channel openers.

It was suggested that the mechanical effects of cromakalim and pinacidil are mediated through the ATP-sensitive K+ channels in the heart

• Creator/s: Defense Technical Information Center
• Date: 1/1/1992
• Year: 1992
• Book Topics/Themes: DTIC Archive, Lau, Wai-Man, DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION CANBERRA (AUSTRALIA), *POTASSIUM, REPRINTS, REDUCTION, VARIATIONS, RESPONSE, MUSCLES, CONTRACTION, GUINEA PIGS, ADENOSINE PHOSPHATES, ATROPINE, PHARMACOLOGY, AUSTRALIA, DISSOCIATION, CHANNELS, HEART

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