Fig. 9.

Quantification of intratesticular RA and correlation of RA concentration and measured RA formation in human testes. Intratesticular atRA and 13-cisRA were measured using LC-MS/MS and a representative chromatogram is shown (A). To confirm peak identity, a MS/MS/MS experiment was conducted and full MS/MS/MS spectra were collected from ion transition m/z 301.2⁺ > 205.3⁺ (B). The spectra shown in (B) are of RA standard and of the three main peaks labeled in (A), 13-cisRA, unknown, and atRA. C: Shows the extracted MS/MS/MS chromatogram of the m/z 301.2⁺ > 205.3⁺ > 159.1⁺ transition. The correlation between formation and atRA or 13-cisRA concentrations in human testis is shown in (D). In addition, total RA had a significant positive correlation with atRA formation.