TEMPERATURE-DEPENDENCE AND PH-DEPENDENCE OF PROTON RELAXATION RATES IN RAT-LIVER TISSUE

In this study proton NMR relaxation rates R(1) and R(2) and pH of untr eated fresh rat liver tissue as well as changes up to 4 h after tissue excision was investigated. Measurements were performed in the tempera ture range from 7 to 45 degrees C. Dynamic changes in all parameters w ere observed at higher temperatures (greater than or equal to 30 degre es C). A qualitatively different time course after tissue excision of all three parameters was obtained for 45 degrees C. The relative alter ations like the change of relaxation rates referred to a reference val ue can predict tissue viability. A good correlation between R(2) and p H in the range of 7-37 degrees C was detected and is described by an i mproved analytical model for R(2) as a function of temperature and pH. The observed data lead to an empirical model given by R(2) (pH,T) = 3 9.8 + (10.2Delta pH) + (0.1*Delta T) + (0.2*Delta pH Delta T), where the reference pH value was chosen 7.4 and the reference temperature va lue 37 degrees C (310.15 K), respectively.