Ryanodine decreases internal Ca2+ recirculation fraction of the canine heart as studied by postextrasystolic transient alternans

The Japanese Journal of Physiology
Y HataH Suga

Abstract

We tested our hypothesis that the O2 wasting of Ca2+ handling in the excitation-contraction (E-C) coupling in ryanodine-treated failing hearts could be reflected by a decrease in the internal Ca2+ recirculation fraction (RF). We have reported, using canine excised cross-circulated hearts, that intracoronary ryanodine (40 nmol/l blood) halved left ventricular contractility without decreasing myocardial O2 consumption for the E-C coupling. We previously suspected this mechanoenergetic state to manifest energy wasting of Ca2+ handling due to ryanodine causing leakage of Ca2+ from the sarcoplasmic reticulum. To test this hypothesis, we analyzed all the sporadic spontaneous cases of postextrasystolic potentiation (PESP) obtained during the ryanodine experiments. We calculated RF from the beat constant of the exponential decay component of not only the monotonic type but also the transient alternans type of PESP. Results showed that ryanodine significantly decreased the beat constant in both types of PESP from about 2 to 1.5 beats and hence RF from 0.6 to 0.5 on the average, supporting the hypothesis. This organ-level systems approach to Ca2+ handling using transient alternans PESP as well as monotonic PESP may help obtain better ins...Continue Reading

Citations

Oct 30, 1999·Heart and Vessels·J MizunoH Suga
Jul 6, 2000·The Japanese Journal of Physiology·T TakasagoH Suga
Dec 20, 2000·The Japanese Journal of Physiology·M MaesakoH Suga
Nov 11, 2003·The Japanese Journal of Physiology·Juichiro ShimizuHiroyuki Suga
Jan 6, 2005·The Japanese Journal of Physiology·J MizunoH Suga
Dec 2, 2004·Experimental Physiology·D A EisnerA W Trafford
Nov 1, 2005·Journal of Biomechanics·Mark I M NobleAngela J Drake-Holland
Feb 24, 2001·Canadian Journal of Physiology and Pharmacology·J ArakiH Suga
Apr 25, 2000·American Journal of Physiology. Heart and Circulatory Physiology·S LeeH Suga
Jan 15, 2002·American Journal of Physiology. Heart and Circulatory Physiology·Ju MizunoHiroyuki Suga
Jul 19, 2000·American Journal of Physiology. Heart and Circulatory Physiology·J ShimizuH Suga
Jul 17, 2001·American Journal of Physiology. Heart and Circulatory Physiology·H KohzukiM Takaki

❮ Previous
Next ❯

Related Concepts

Related Feeds

Cardiac Cachexia

Cardiac cachexia is a syndrome associated with the progressive loss of muscle and fat mass. It most commonly affects patients with heart failure and can significantly decrease the quality of life and survival in these patients. Here is the latest research on cardiac cachexia.

Cachexia & Brown Fat

Cachexia is a condition associated with progressive weight loss due to severe illness. In cancer patients, it is proposed to occur as a result of tumor-induced energy wasting. Several proteins have been implicated in browning and depletion of white adipose tissue. Here is the latest research on cachexia and brown fat.