An experimental approach to 31P spin-lattice relaxation time measurement in biological systems

The accuracy of measurement of the spin-lattice relaxation time (T1) in biological systems using the variable nutation angle method is discussed using computer simulations. This method could reduce the time required for measurement to 10% of that using the inversion recovery method. In the perfused salivary gland of the rat (310 K), the T1 values of sugar phosphates, creatine phosphate, gamma-phosphate, and beta-phosphate of nucleotide triphosphates determined by this method were 5.2, 4.8, 0.9, and 0.8 s, respectively. During secretion of saliva, the T1 value of sugar phosphates decreased to 3.7 s, which could be due to an increased chemical exchange of phosphate in glycolysis.