Figure 4.

Body composition analysis in γ^mt/mt and γ^+/+ mice reveals differences in body water and lean tissue mass in response to changes in dietary salt. Body composition was measured using quantitative magnetic resonance in 9- to 14-wk-old mice. Starting weights were similar between groups. Before dietary manipulation, there were no differences in body composition as a percentage of total body weight. Mice were placed on a Na⁺-depleted (0.01−0.02% Na⁺) diet, and subsequent body composition variables were normalized to baseline for each animal. By day 2, normalized total body water was lower in γ^mt/mt mice than in γ^+/+ mice (P < 0.05). Normalized lean tissue mass was also lower in γ^mt/mt mice (P < 0.01). Normalized fat content did not differ between γ^+/+ and γ^mt/mt mice. Composition did not differ on subsequent days. After a 10-day recovery on regular diet, the effect of 2% saline on body composition was evaluated. On day 2, normalized body water and lean tissue had increased in γ^mt/mt mice compared with the controls (P < 0.05 for each). Thereafter, composition did not differ between genotypes. Body fat did not differ between genotypes. Statistical significance of differences between genotypes on a given day was assessed via a two-tailed t test. *P < 0.05; **P < 0.01.