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CARDIAC GLYCOGEN AND THE EFFECT OF GROWTH HORMONE AMONG INBRED STRAINS OF MICE¹

Department of Biochemistry, Division of Basic Health Sciences, Emory University Georgia

Abstract

In an effort to detect differences in the peripheral activity of growth hormone among C⁵⁷, A, C³H, and I strain mice, the concentrations of cardiac glycogen were determined during the course of a 24-hour fasting period, and in three different age groups (young, 40–50 days; young-adult, 3–5 months; and old, 8–13 months). The concentrations and changes in cardiac glycogen were found to be characteristic of the age, and of the strain of mice. For example, in youngadult, but not young, mice of the I strain, cardiac glycogen actually decreased during a 24-hour fast. Some strain differences were found, but these were not consistent in all age groups. It was concluded that cardiac glycogen was subject to a variety of influences, which in turn varied with the age of the animal.

As found for the rat, exogenous growth hormone doubled the stores of cardiac glycogen but the hormone had to be administered in the morning to nonfasted mice. If it was administered in the afternoon, it was not effective. This, and other evidence, suggests that insulin is required for the action of growth hormone on cardiac glycogen deposition.

Footnotes

¹ This study was supported in part by a research grant (A-1264) from the National Institute of Arthritis and Metabolic Diseases, Public Health Service.

² Life Insurance Medical Research Fellow (1954-56) and Lederle Medical Faculty Award (1956–59).

Received October 10, 1958.