Effectiveness of theophylline to increase cyclic AMP levels and force of contraction in electrically paced guinea-pig auricles. Comparison with isoprenaline, calcium and ouabain

The effects of theophylline (3×10−5 M–5×10−3 M), isoprenaline (10−6 M), excess calcium (7.2 mM) and ouabain (3×10−7 M) on force of contraction and c-AMP content were studied in electrically driven (frequency 3 Hz) left auricles isolated from guinea pigs pretreated with reserpine.