Analysis of muscular development of mice at high gravity

¹ Department of Physiology and Biochemistry, Rutgers-The State University, New Brunswick, New Jersey, and Department of Physiology, State University of Iowa, Iowa City, Iowa

Although 4 g, as simulated by continual centrifugation, delays growth of the heart, diaphragm, and gastrocnemius muscles, some growth of these organs is possible at this gravitational field. Over-all body growth actually suffers a more marked retardation than do these experimental organs. Results are for both sexes of NLW white mice, whose exposure was initiated at the age of 5 weeks. The fractional water content was almost constant throughout, being only slightly lower in the experimental muscles. Analysis for noncollagen-nitrogen (NCN) was employed as an index of contractile and sarcoplasmic proteins. Throughout the experiment, concentration of NCN was below the control level in the diaphragm tissue. For the heart, the fraction was 26 ± 12% below normal after 2 weeks of centrifugation. However, the NCN concentrations were not measurably changed in the heart after 1, 4, and 8 weeks of centrifugation; moreover, throughout the experiment, there were no measurable changes of NCN concentration for the gastrocnemius muscles. Although muscular growth would be possible in a gravitational field exceeding the terrestrial intensity, some alteration in the type of musculature would be expected.