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Differential effects of organic calcium‐channel blockers on diastolic SR calcium‐handling in the frog heart
Author(s) -
Subramani Sathya,
Vijayanand Caroline,
Tharion Elizabeth
Publication year - 2002
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.0704921
Subject(s) - verapamil , diltiazem , nifedipine , calcium , beat (acoustics) , medicine , chemistry , endocrinology , calcium channel , rest (music) , propranolol , physics , acoustics
Gradual loss of sarcoplasmic reticular (SR) calcium during a rest‐period is responsible for the rest‐induced decay (RID) of force in mammalian myocardium. Effect of verapamil and diltiazem on a similar RID in the frog myocardium suggests a new mechanism of action of these drugs. Strips of frog‐ventricle were paced at 0.2 Hz and the rhythm was interrupted by varying rest‐periods ranging from 10 to 180 s. In control conditions, the amplitude of the post‐rest beat was significantly lower than that of the pre‐rest beat for rest‐periods more than 40 s (RID). Verapamil and diltiazem (which are organic calcium‐channel blockers (OCCB)) changed the pattern of RID in the control solution to a ‘rest‐induced potentiation’ (RIP) in the same preparation while another OCCB nifedipine and the inorganic calcium‐channel blocker cadmium did not alter the post‐rest phenomenon. We propose that verapamil and diltiazem produce an RIP due to either blockade of SR calcium‐leak during rest or enhancement of SR calcium‐uptake during rest.British Journal of Pharmacology (2002) 137 , 756–760. doi: 10.1038/sj.bjp.0704921