NMR in cancer: VIII. Phosphorus-31 as a nuclear probe for malignant tumors.

Spin-lattice relaxation times (T1) for 31P were determined in normal and malignant tissues by a saturation technique employing a 90 degree -tau-90 degrees pulse sequence. Results for five normal tissues from rat were (in seconds): 2.33 +/- .14 for liver; 2.19 +/- .05 for muscle; 1.13 +/- .05 for brain; 1.43 +/- .15 fro kidney; and 1.97 +/- .12 for intestine. Results for two rat malignancies, Novikoff hepatoma and Walker sarcoma, were 5.98 +/- .57 and 5.38 +/- .68, respectively, and for Crocker sarcoma of mouse, 5.19 +/- 1.42. No individual measurement of malignant tissue overlapped any of the normal measurements; probabilities of insignificance ranged from .029 for Crocker sarcoma to .000184 for Novikoff hepatoma. The data call attention to another nucleus of potential value for NMR detection of internal malignancies in humans. Also suggested, because of the strategic placement of the 31P nucleus in the nucleic acid molecule, is a possible new probe for exploring the mechanism of carcinogenesis.