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COMPARISON OF EFFECTS OF GLUCAGON AND ISOPRENALINE ON ATRIO‐VENTRICULAR CONDUCTION AND SINO‐ATRIAL RATE IN THE DOG HEART
Author(s) -
Iijima Toshihiko,
Motomura Shigeru,
Taira Norio,
Hashimoto Koroku
Publication year - 1974
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1974.tb00546.x
Subject(s) - isoprenaline , chronotropic , medicine , heart rate , endocrinology , chemistry , glucagon , atrioventricular node , tachycardia , blood pressure , hormone , stimulation
SUMMARY 1. The effects of glucagon and l ‐isoprenaline on atrio‐ventricular (A‐V) conduction and sino‐atrial (S‐A) rate were studied in the isolated and cross‐circulated canine A‐V and S‐A node preparations. Drugs were injected intravenously into the donor dog. 2. l ‐Isoprenaline (0.01–3 nmol/kg) caused a dose‐dependent decrease in the A‐V conduction time and an increase in the S‐A rate. In doses larger than 0.3 nmol/kg, a ventricular ectopic rhythm was provoked in the A‐V node preparation. Dose‐response curves for the changes in A‐V conduction time and the S‐A rate produced by l ‐isoprenaline were almost parallel and the responses were maximal with 3 nmol/ kg. 3. Glucagon (0.03–3 nmol/kg) also caused a decrease in the A‐V conduction time and an increase in the S‐A rate in a dose‐dependent manner, but unlike l ‐isoprenaline, it did not provoke a ventricular ectopic rhythm in the A‐V node preparation even in large doses. The decrease in the A‐V conduction time was maximal with 3 nmol/kg, whereas the increase in the S‐A rate was not more than 50% of the maximum with this dose. 4. The durations of the responses to glucagon were increased in a dose‐dependent manner and were far longer than those to l ‐isoprenaline in equimolar doses. The positive chronotropic effect of glucagon was less than that of l ‐isoprenaline, not only in the S‐A node preparation, but also in the donor dog. 5. The findings suggest that glucagon may serve as a valuable agent in clinical medicine for decreasing A‐V conduction time.