Biological implications of androgen dependent changes in proton-NMR relaxation times in rat ventral prostate

The present studies were conducted in rat ventral prostate to determine if proton nuclear magnetic resonance (1H-NMR) might be a useful tool to monitor physiologic changes in an androgen-dependent target tissue after ablation and reconstitution. Ventral prostate mass and blood flow (86RbCl distribution) decreased markedly after castration. Although prostate water content was not affected by androgen ablation, 1H-NMR spin-lattice (T1) and spin-spin (T2) relaxation times determined on excised prostate tissue were reduced by 10% and 50%, respectively. Testosterone propionate (Tp) reconstitution resulted in a prompt but transient increase in total water content, marked increases in prostate blood flow, and regrowth of the gland. 1H-NMR studies indicated that although T1 lengthening after Tp was temporally related to changes in prostate water content, T1's remained prolonged after total prostate water content returned to control levels. Increased Gd-DTPA-dimeg modification of prostate T1 by Gadolinium-DTPA-dimethyl glucamine in androgen reconstituted rats implied that prostate extracellular water volumes were markedly increased during intervals of increased T1. Recovery of prostate T2 relaxation times after Tp was delayed with respect to changes in T1, water content, and prostate blood flow, but was temporally correlated with increase in prostate dry mass. Studies to assess Gd-DTPA-dimeg T2 modification showed that prostate T2 changes after androgen depletion and replacement reflected spin-spin relaxation of water protons outside the in vivo Gd-DTPA-dimeg distribution volume. The results from these studies indicate that 1H-NMR and paramagnetic probes may be useful to noninvasively monitor biologically relevant changes in cellular and extracellular water in androgen-dependent target tissues during hormonal manipulations.