Linear rate of change in the product of erythrocyte water content and potassium concentration during the 0-120-hour postmortem period in the rat.

An accurate and reproducible technique was employed for measurement of water content (RBCH2O) and potassium concentration (RBCK) in rat erythrocytes post mortem. Coefficients of variation for determination of RBCH2O and RBCK, as estimated from the results of duplicate analyses (n = 36), were 1.21% and 1.17%, respectively. Erythrocyte water content and RBCK were directly and linearly related (r = +0.93 (P less than 0.001], while the product of RBCH2O and RBCK varied linearly and inversely (r = -0.89 (P less than 0.001] with postmortem interval (PMI) over the 0-120-h postmortem period. In addition, the standard deviations of the data points for (RBCH2O X RBCK) remained relatively constant and independent of PMI. Attention is drawn to the possibility of determining time elapsed since death from (sequential) measurements of (RBCH2O X RBCK) in individual cadavers.