Evaluation of developing rat testis by phosporus 31P magnetic resonance spectroscopy and DNA flowcytometry

For the assessment of germ-cell maturation of the seminiferous tubules, DNA flowcytometry is a rapid and sensitive method. Phosporus 31P magnetic resonance spectroscopy (MRS) is a non-invasive alternative that demonstrates the metabolic status of the testis, reflecting the type and relative proportion of germ cells in the testis. This study was designed to evaluate the utility of 31P MRS in reflecting the haploid-cell population of the testis as measured by DNA flowcytometry. A single testicle was evaluated in male Wistar pre-pubertal rats at 30, 40, 50, and 60 days of age. In order to minimize the contamination of signals from the contralateral testis, scrotum, and tail, the technique was modified and the testis was evaluated ex-vivo with an intact blood supply. At 30 days of age the percentage of haploid cells was 43.6 +/- 1.8, and this increased to 72.7 +/- 1.4 at 60 days of age. During this period, the testicular phosphomonoester/adenosine triphosphate (PM/ATP) ratio changed from 1.70 +/- 0.21 to 0.32 +/- 0.08. There was a significant (P < 0.001) linear correlation between the proportion of haploid cells evaluated by DNA flowcytometry and the PM/ATP ratio evaluated by 31P MRS. 31P MRS is thus a reliable, noninvasive technique for accurately assessing the status of the seminiferous epithelium.