Intraspecies allometry: correlation between kidney weight and glomerular filtration rate vs. body weight

Allometric equations of the form of Y = a*BWb were calculated between body weight (BW) on the one hand and either kidney weight (KW) or glomerular filtration rate (GFR) on the other. By using strain and sex means obtained from 24 different inbred strains of adult mice or F1-hybrids environmental and genetical influences could be separated statistically. Thus, allometric equations reported in this study describe exclusively genetic influence. The parameters for intraspecies allometric equations obtained in these studies were compared to those in the literature presenting interspecies relationships. The double logarithmic regressions of KW vs. BW gave results different from the interspecies equation. The difference between intra- and interspecies results of allometric relationships may be due to the experimental exclusion of environmental influences. The regression parameters for GFR vs. BW obtained for the inbred strains, however, agreed very well with those of the empirical equation for interspecies relationship and also with the theoretically expected value. The dependence of GFR on BW was found to be GFR = 0.036*BW0.74 +/- 0.15, where GFR is measured in ml/min and BW in g. The exponent of 0.74 seems to be a valid biological constant that is genetically determined within and across species lines.