The effect of experimental cryptorchidism on the phosphorus NMR spectrum of the rat testis.

Magnetic resonance (MR) spectroscopy of the cryptorchid rat testis was used to test whether changes in the MR spectra of the rat testis might be a more sensitive indicator of changes in the metabolic status of germ cells in the testis rather than simply the cell types present. Testes of adult Wistar rats before and during 42 days of experimental cryptorchidism were investigated by in-vivo 31P MR spectroscopy. Results were compared to MR studies of the synchronized developing testis. The testicular phosphomonoester/ATP (PM/ATP) ratio was dependent only on the cell types present, and showed the same characteristics for each cell type present in the degenerating testis as in the developing testis. The testicular phosphodiester/ATP (PD/ATP) ratio decreased rapidly when the number of round and elongated spermatids was reduced. Similar effects, although less pronounced, were seen in the developing testis. The pH decreased rapidly after cryptorchidism, and was related inversely to the PM/ATP ratio, which was also observed in the developing testis. This study demonstrates that MR spectroscopy monitors the cell types present in the rat testis rather than its metabolic status.