Glycogen Content of the Rat Heart

Abstract

The cardiac glycogen of albino rats has been determined under a variety of conditions. The figures quoted are for glycogen as glucose in milligrams percent, and unless otherwise stated are for 24-hour fasted animals. Amytal anesthesia was used when securing hearts and muscles.

Fifty-two 24-hour fasted animals, used as controls, showed a quite constant cardiac glycogen of 497±56 mg. %; the gastrocnemii of the same animals contained 525 ±48 mg. %.

Animals fasted for 48 hours had more glycogen in the hearts (578±81) and less in the gastrocnemii (455±37) than controls.

Non-fasted animals showed considerably less cardiac glycogen (341±54) but more glycogen in gastrocnemii (574±74) than controls.

It was found also, that 24-hour fasted animals which had been fed sufficient glucose by mouth to provide for maximum absorption for 4 hours, and which were taken at the end of such time, had somewhat less glycogen in the hearts (449±50), although considerably more in the gastrocnemii (690±48) than controls. When, however, insulin injection accompanied such glucose feeding, both hearts and gastrocnemii contained increased glycogen (hearts 703± 212, gastrocnemii 830±183).

Epinephrine sufficient to reduce the glycogen of gastrocnemii to 55% of its control value did not alter cardiac glycogen appreciably. The cardiac glycogen after subcutaneous injection of 0.02 mg. of epinephrine per 100 gm. of rat, was (a) in 1/2 hour 475±52, (b) in 3 hours 509±54. One-half hour after large intravenous doses of epinephrine the hearts contained 475±26.

Similarly, exercise, both natural and electrically produced, sufficient to reduce the glycogen of gastrocnemii to 70% of its control value did not decrease cardiac glycogen, the values being (a) after natural exercise 546±40, (b) after electrical stimulation 512±19. When, however, electrical stimulation was severe enough to produce cyanosis through interference with respiratory movements the cardiac glycogen was much reduced, being 226±33.