Body surface areas and K values in strain 13 guinea pigs with different body weights and ages

Body surface areas (BSA) were determined for strain 13 guinea pigs with body weights ranging from 191 to 1011 g. For this determination, the entire skin of each animal was removed immediately after death and flattened on a wax film with a homogeneous paper. The skin outlines on the paper were cut and weighed for determining BSA. The K value was calculated for each guinea pig as the ratio of BSA (cm2)/body weight (g)2/3. Significantly different K values of 11.31 +/- 0.11, 9.66 +/- 0.09, 9.22 +/- 0.05, and 9.17 +/- 0.05 were determined for average body weights of 218 +/- 24, 527 +/- 33, 706 +/- 60, and 943 +/- 30 g, respectively. By plotting these K values on semilog paper and determining the best fit curve of the slope, it was possible to extrapolate exponentially the K values for different body weights. The relationship between age and body weight was also established for guinea pigs, and a series of K values were determined from birth to 35 weeks of life. We conclude that a different K value should be used for calculating BSA for various ages and body weights of strain 13 guinea pigs.