Chemical maturation in growing guinea pigs.

Twenty-seven guinea pigs were analyzed chemically for total body water (TBW), fat, nitrogen (N), calcium (Ca), and sodium (Na); 26 were analyzed for potassium (K). Body weights ranged between 82 and 877 g. The data were analyzed by regression analysis. If the slope of a regression line did not differ significantly from zero (P less than 0.05), the mean and standard deviation were calculated. The slopes of the regression lines were significant for Na [meq/100 g fat-free wet weight (FFWW)] on body weight in grams, K in milliequivalents on FFWW in grams, and total body fat (TBF) (g) on body weight in grams. The means and standard deviations for the remaining constituents were in g/100 g FFWW; 76.0 +/- 2.5 for TBW and 2.52 +/- 0.28 for N, and in meq/100 g FFWW Ca 58.26 +/- 7.35 and K 6.35 +/- 0.74, and % TBF 8.57 +/- 3.44. The values for the following ratios were: K/N 2.609 +/- 0.247; K/TBW 0.087 +/- 0.011; and N/TBW 0.033 +/- 0.004 (K is in meq, N and H2O in g). The suggestion that the lower figure for TBW reported by earlier investigators compared to the present data could be the result of a systematic methodological error is discussed.