Apr 1, 1989

Combined effects of hypoxia and elimination of glucose on resting and postextrasystolic potentiated contractions of papillary muscle of guinea pigs

Japanese Circulation Journal
J AsayamaM Nakagawa

Abstract

We studied the combined effects of hypoxia and the absence of glucose on postextrasystolic potentiated and resting contractions in papillary muscle of guinea pigs. Postextrasystolic potentiations (PESPs) were evoked following trains of 40 externally applied continuous stimulations. During hypoxia resting (regular) contractions decreased to about 25% of baseline tension at 30 degrees C, whereas postextrasystolic potentiated contractions decreased to about 35% of baseline measurement of postextrasystolic potentiated contraction. In contrast, with reoxygenation, PESPs recovered quickly while resting contractions recovered gradually. Caffeine abolished the potentiation of post-extrasystolic contraction not only in normoxia but also in hypoxia. We speculate that calcium release from the sarcoplasmic reticulum (SR) is attributable to PESP for the most part, and that the trans-sarcolemmal calcium influx generally contributes to the steady-state tensions developed by continuous stimulations. In addition, it seems that PESP works in a ischemic heart to compensate for the decreased tension during hypoxia as a potentiation by a premature ventricular contraction. Trans-sarcolemmal calcium influx might be affected more easily than the SR ca...Continue Reading

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Mentioned in this Paper

Myocardial Contraction
DRUG Screen Quant Caffeine
Calcium [EPC]
Dioxygen
Calcium
Cavia
Quick-Pep
Contraction (Finding)
Glucose, (beta-D)-Isomer
Sarcoplasmic Reticulum

About this Paper

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