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

The accuracy of measurement of the spin‐lattice relaxation time ( T 1 ) 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 T 1 values of sugar phosphates, creatine phosphate, γ‐phosphate, and β‐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 T 1 value of sugar phosphates decreased to 3.7 s, which could be due to an increased chemical exchange of phosphate in glycolysis. © 1988 Academic Press, Inc.