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A rapid and highly sensitive liquid chromatography/electrospray ionization tandem mass spectrometric method (LC/ESI-MS/MS) for itraconazole determination in human plasma was validated and applied to pharmacokinetic and bioequivalence study in humans. In a randomized crossover design with a 1-week period, each subject received a 200 mg itraconazole capsule. The analytical procedures involved a less time-consuming, simple protein precipitation with methyl t-butyl ether and separation by HPLC. The ionization was optimized using electrospray ionization (ESI) with positive ion mode and selectivity was achieved by MS/MS analysis, m/z 705.3 --> 392.4 and m/z 374.3 --> 141.0 for itraconazole and internal standard (IS), respectively. The standard calibration curves showed good linearity within the range of 1 (LLOQ) to 500 ng/mL for itraconazole in human plasma with a correlation coefficient r > 0.9952. The retention times of itraconazole (0.9 min) and IS (0.84 min) suggest the high throughput of the proposed method. No significant metabolic compounds were found to interfere with the analysis. The coefficient of variation values of both intra- and inter-day were below 13.7% and 10.9%, respectively. Intra- and inter-day accuracies were 95.6-108.2% and 86.6-117.5%, respectively. This method was successfully applied for pharmacokinetic and bioequivalence study in 24 healthy human subjects by analysis of blood samples taken up to 72 h after an oral dose of 200 mg of itraconazole.

We previously showed that Asb-4 and Asb-17 is uniquely expressed in developing male germ cells. A recent report showed that Asb-9 is specifically expressed in the kidney and testes; however, detailed expression patterns in developing germ cells have not been shown. Northern blot analysis in various tissues demonstrated that mAsb-9 was strongly expressed in the testes. Expression analysis by RT-PCR and Northern blot in developing mouse testes indicates that mAsb-9 is expressed from the fourth week after birth to adulthood, with the highest expression in round spermatids. Expression sites were further localized by in situ hybridization in the testes. Pachytene spermatocytes and spermatids expressed mAsb-9 but spermatogonia and generated spermatozoa did not. This study reveals that mAsb-9 could be a specific marker of active spermatogenesis and would be useful for studies of male germ cell development.

Members of the large family of Asb proteins are ubiquitously expressed in mammalian tissues; however, the roles of individual Asb and their function in the developmental testes have not been reported. In this report, we isolated a murine Asb4 from mouse testis. Northern blot analysis revealed that mAsb-4 was expressed only in testes and produced in a stage-specific manner during spermatogenesis. It was expressed in murine testes beginning in the fourth week after birth and extending into adulthood. Pachytene spermatocytes had the highest level of expression. Interestingly, the human homologue of mAsb-4, ASB-4 (hASB-4) was also expressed in human testis. These results suggest that ASB-4 plays pivotal roles in mammalian testis development and spermatogenesis.