Studies on oral bioavailability and first-pass metabolism of withaferin A in rats using LC-MS/MS and Q-TRAP.

Withaferin A (WA) is one of the major bioactive steroidal lactones with extensive pharmacological activities present in the plant Withania somnifera. The absolute oral bioavailability of WA remains unknown and human-related in vitro data are not available. Therefore, in the present study, the absolute oral bioavailability of WA in male rats and the in vitro screening of absorption factors by Q-trap and LC-MS/MS analysis were conducted to explore possible clinical properties of WA. The developed and validated analytical methods were successfully applied to the pharmacokinetic studies and in vitro measurement of WA. The oral bioavailability was determined to be 32.4 ± 4.8% based on intravenous (5 mg/kg) and oral (10 mg/kg) administrations of WA in male rats. The in vitro results showed that WA could be easily transported across Caco-2 cells and WA did not show as a substrate for P-glycoprotein. Moreover, the stability of WA was similar between male rat and human in simulated gastric fluid (stable), in intestinal microflora solution (slow decrease) and in liver microsomes (rapid depletion, with a half-life of 5.6 min). As such, the first-pass metabolism of WA was further verified by rat intestine-liver in situ perfusion, revealing that WA rapidly decreased and 27.1% remained within 1 h, while the content of three major metabolites (M1, M4, M5) identified by Q-trap increased. This perfusion result is consistent with the oral bioavailability results in vivo. The first-pass metabolism of WA might be the main barrier in achieving good oral bioavailability in male rats and it is predicted to be similar in humans. This study may hold clinical significance.

Effect of liquid helium vitrification on the ultrastructure and related gene expression of mature bovine oocytes after vitrifying at immature stage.

This study aimed to investigate the developmental potential of and the ultrastructural changes and gene expression differences resulting from liquid helium (LHe; -269 °C) vitrification in immature bovine oocytes. Immature oocytes were randomly divided into three groups: fresh oocytes (control, negative control), oocytes vitrified in liquid nitrogen (LN group, positive control), and oocytes vitrified in LHe (LHe group). In experiment 1, the rates of normal morphology, maturation, cleavage, and blastocyst in the LHe group were higher than those in the LN group (87.1% vs. 80.5%, 51% vs. 48%, 41.7% vs. 36.8%, and 13% vs. 8.5%, respectively; P < 0.05), and the rates of development in the control group (100%, 73.2%, 62%, and 39.8%) were higher than those in the treated groups (P < 0.05). In experiment 2, oocytes displayed various degrees of injury at the ultrastructural level after vitrification, but more severe degeneration was observed in the LN group, such as formation of several lipid droplets, swelling of mitochondria, and absence of cortical granules. Compared with the LN group, fewer lipid droplets, relatively intact mitochondria, and clustered cortical granules were distributed in the cytoplasm of oocytes in the LHe group. In experiment 3, the mRNA expression levels of p53, CDC20, Eg5, and Npm2 were investigated by real-time quantitative polymerase chain reaction. Expression levels of the kinesin Eg5 and the apoptotic gene p53 expression levels were higher in the LN group compared with the control and LHe groups (P < 0.05). CDC20 and Npm2 expression did not differ significantly between the LN and LHe groups (P > 0.05), the CDC20 expression in the LN and LHe groups were lower than control group (P < 0.05), the Npm2 expression in LHe group was lower than control group (P < 0.05), but there was no significant difference between the LN and control groups (P > 0.05). In conclusion, LHe vitrification decreased the negative effect of cryoinjury on the ultrastructure of some organelles and the expression of some related genes, thereby improving the viability of immature bovine oocytes compared to LN vitrification.