Modulation of porcine cytochrome P450 enzyme activities by surgical castration and immunocastration

Abstract

The present study aimed to evaluate some cytochrome P450 metabolic enzyme activities in hepatic microsomes prepared from entire male pigs (uncastrated pigs), surgically castrated pigs and pigs immunized against gonadotropin-releasing hormone (immunocastrated pigs). The activities of the following enzymes were measured: ethoxyresorufin O-deethylase (EROD, CYP1A1/ 1A2), methoxyresorufin O-deethylase (MROD, CYP1A2), pentoxyresorufin O-depentylase (PROD, CYP2B), coumarin hydroxylase (COH, CYP2A) and p-nitrophenol hydroxylase (PNPH, CYP2A/2E1). The total cytochrome P450 contents were not affected by either surgical or immunocastration. Hepatic microsomal activities for EROD, PROD, COH and PNPH were lower in entire male pigs compared with surgically castrated and immunocastrated pigs ( P , 0.05). Surgically and immunocastrated male pigs were similar with respect to EROD, MROD, PROD and COH activities ( P . 0.05), whereas surgically castrated pigs exhibited lower PNPH activity compared with immunocastrated pigs ( P 5 0.029). The effect of different concentrations of testicular steroidstestosterone, 17b-estradiol, free estrone and androstenone -on enzyme activities was evaluated by in vitro microsomal study. Testosterone at the concentration of 8 pmol/ml inhibited EROD activities and estradiol-17b at the concentration of 1.8 pmol/ml inhibited PROD activities in hepatic microsomes from surgically castrated pigs. The highest concentration of androstenone (7520 pmol/ml) inhibited COH activities, whereas a 42-fold lower concentration of androstenone (180 pmol/ml) stimulated COH activities in surgically castrated pigs. Both free estrone (3.5 pmol/ml) and androstenone (55 pmol/ml) inhibited EROD activities in microsomes from entire male pigs. Stimulation of COH activities by the highest dose of free estrone (18 pmol/ml) was recorded in microsomes from entire male pigs. However, these effects of steroids were not concentration-dependent and the maximum extent did not exceed 615% variation compared with the controls. There was no inhibition of PNPH activities in the hepatic microsomes from either entire or castrated pigs. In conclusion, we showed that EROD, PROD, COH and PNPH activities were lower in entire male pigs compared with those in surgically and immunocastrated pigs. Direct inhibition by the testicular steroids -testosterone, 17b-estradiol, free estrone and androstenone -was not the primary cause of the reduced enzyme activities.Keywords: castration, cytochrome P450, porcine liver microsomes, steroids ImplicationsThe present study evaluated some cytochrome P450 enzyme activities in liver microsomes from uncastrated male pigs, surgically castrated pigs and pigs immunized against gonadotropin-releasing hormone (immunocastrated pigs). We found that CYP1A1, CYP2A, CYP2B and CYP2E1 activities were lower in uncastrated male pigs compared with surgically castrated and immunocastrated pigs. These findings strengthen the hypothesis of testicular steroid involvement in cytochrome P450 enzyme regulation. The differences in the ac...

Androgen-mediated down-regulation of CYP1A subfamily genes in the pig liver

“…More recently, we have found a sex difference in the constitutive expression of hepatic CYP1A subfamily enzymes, CYP1A1 and CYP1A2, in Meishan pigs, and further suggested an androgen-dependent downregulation of these genes (Kojima et al 2008). Furthermore, it has been reported that the alteration in plasma testosterone levels in male pigs treated with human chorionic gonadotropin (Zamaratskaia et al 2010) or immunized against GnRH (immunocastrated pigs) (Zamaratskaia et al 2009) led to modulation of hepatic activities of CYP1A subfamily enzymes. Likewise, androgen is also considered to be one of the factors which determine sexual dimorphism in the constitutive and/or xenobiotic-induced expression of Cyp1a2 (Hashimoto et al 1982, Degawa et al 1985, Cyp2b (Honkakoski et al 1992), and Cyp4b1 (Degawa et al 1990, Imaoka et al 1995 in mice.…”

Impact of age on hepatic cytochrome P450 of domestic male Camborough‐29 pigs

“…This activity is not detectable in the porcine liver microsomes at the age of 1 day and 2 weeks of intact males, but detected at a significant level in castrated males at the age of 5 weeks, and then rapidly increases with growth. This is consistent with the significant increase in CYP2A mRNA expression, protein, and enzyme activity levels after removal of the primary androgen source (Gillberg et al ., ; Chen et al ., ; Zamaratskaia et al ., ; Brunius et al ., ) in addition to the age effect.…”

Influence of sex and immunocastration on feed intake behavior, skatole and indole concentrations in adipose tissue of pigs

“…In immunocastrates with an overall high feed intake rate significantly higher indole concentrations were measured than in all other groups. It is known that the levels of enzymes that are involved in the degradation of skatole (CYP2E1 and CYP2A) are increased in barrows and immunocastrates when compared with the levels in boars (Zamaratskaia et al, 2009;Brunius et al, 2012). In vitro studies with porcine hepatocytes revealed that the addition of androstenone in physiological amounts reduced the activity of both enzymes (Doran et al, 2002b;Rasmussen et al, 2011).…”