A quantitative property-property relationship (QPPR) approach to estimate in vitro tissue-blood partition coefficients of organic chemicals in rats and humans

The present study describes quantitative property-property relationships (QPPRs) for the partitioning of organic chemicals between blood and tissue homogenates from both rats and humans. The n-octanol/water partition coefficient (k(ow)) is used as a nonbiological descriptor. QPPRs for human tissue-blood partition coefficients (PCs) were derived from a dataset of 24 volatile organic compounds in blood, liver, muscle, fat, kidney and brain tissue homogenates. QPPRs were also derived for the PCs of rat tissues, using a dataset of 42 volatile organic compounds in blood, liver, muscle and fat tissue homogenates. These QPPRs were evaluated using a test set of 10 compounds for human tissues and a test set of 14 compounds for rat tissues. For both human and rat test sets, it was generally observed that most estimated PCs were within a range of 50-200% of their experimental values. The present approach is concluded to offer a rapid means for the estimation of tissue-blood PCs of compounds on the basis of k(ow), values. In addition, indications for a possible role of tissue components other than lipid and water in the tissue-blood partitioning process of compounds were observed from the calibration results of the model.