Expression of 3-hydroxysteroid dehydrogenase, cytochrome P450c17 and sulfotransferase 2B1 proteins in liver and testis of pigs of two breeds: relationship with adipose tissue androstenone concentration

¹ NORSVIN, P.O. Box 504, 2304 Hamar, Norway; Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway
² NORSVIN, P.O. Box 504, 2304 Hamar, Norway
³ Division of Farm Animal Science, School of Clinical Veterinary Science, University of Bristol, Langford, Bristol, BS40 5DU, UK

^* To whom correspondence should be addressed. E-mail: o.doran{at}bristol.ac.uk.

	Abstract

An excessive accumulation of androstenone in pig adipose tissue is a major contributor to the phenomenon of boar taint. Androstenone deposition is dependent on the rate of androstenone biosynthesis in testis and androstenone degradation in liver. The aim of the present study was to examine the possibility of the existence of breed-specific mechanisms controlling androstenone accumulation in pig adipose tissue. The specific objective was to investigate the expression some of the key enzymes involved in the testicular and hepatic androstenone metabolism in pigs of two breeds, using animals with high and low androstenone concentrations within each breed. The study was conducted with Norwegian Landrace (N. Landrace) and Duroc boars. The average androstenone values for low- and high-androstenone groups were: 0.1 ± 0.01 µg/g and 7.58 ± 0.68 µg/g for N. Landrace boars; 0.22 ± 0.04 µg/g, and 13.55 ± 1.14 µg/g for Duroc boars. The enzymes investigated were: 3-hydroxysteroid dehydrogenase (3-HSD), cytochrome P450-c17 (CYP17) and sulfotransferase 2B1 (SULT2B1). It has been established that expression of CYP17 in liver and testis did not differ between animals with high and low androstenone concentrations in either N. Landrace or Duroc breed. Expression of the hepatic 3-HSD, which catalyses the first stage of androstenone degradation, was decreased in high-androstenone N. Landrace (P < 0.01), but not in high-androstenone Duroc pigs. In contrast, the expression of the hepatic SULT2B1, catalyzing the second stage of steroid catabolism, was decreased in high-androstenone Duroc (P < 0.05), but not in high-androstenone N. Landrace animals. Sulfotransferase 2B1 was also inhibited in testis of high-androstenone pigs of both breeds compared with low-androstenone animals. The present study reports breed differences in the expression of androstenone-metabolizing enzymes 3-HSD and SULT2B1 in liver of high- and low androstenone pigs. It is suggested that accumulation of androstenone in adipose tissue of N. Landrace boars might be related to a low rate of the hepatic androstenone degradation in the metabolic stage I, whereas the high androstenone concentration in Duroc boars might be related to a low rate of androstenone metabolism in metabolic stage II.

Key Words: Androstenone, breed, cytochrome P450c17, 3beta-hydroxysteroid dehydrogenase, pig, sulfotransferase 2B1