Post-natal patterns of plasma androgen-binding activity in Djungarian (Phodopus sungorus) and golden (Mesocricetus auratus) hamsters

Abstract

The binding of sex steroids to plasma proteins was examined in post-natal Djungarian and golden hamsters. With dihydrotestosterone or testosterone as ligands, steady-state polyacrylamide gel electrophoresis revealed 2 androgen binding components in the plasma of young Djungarian hamsters of both sexes. The fast-moving component exhibited a low affinity and high capacity for androgens and corresponded to albumin in stained gels. In contrast, the slow moving component was a \g=b\-globulin with high affinity (Ka = 109 m \ m=-\ 1) and low capacity for androgens, and was identified as a specific sex steroid-binding protein (SBP; also SHBG). This SBP did not bind oestrogens or corticosteroids and was electrophoretically distinct from corticosteroid-binding globulin (CBG). In addition, this protein did not appear to be of testicular origin because it was present in immature females and in immature males that had been castrated for 8 days. Plasma concentrations of SBP in males as measured by a diethylaminoethyl-cellulose binding assay were low at birth, became significantly elevated shortly thereafter when plasma androgen values were also elevated, and subsequently fell to low levels during puberty. These changes follow the same general pattern that has been described for other mammals, including humans, during this period of reproductive development. Although the significance of elevated SBP concentrations during prepuberty has yet to be determined, it appears that the increased concentrations of high-affinity androgen binding in the plasma of Djungarian hamsters plays a role in the asynchronous pubertal development of the testes and accessory organs which occurs in this species. The post-natal SBP pattern in females was similar to that observed in males. Plasma SBP levels were low or undetectable in adults of both sexes. As previously described for adult golden hamsters, the plasma of post-natal male and female golden hamsters lacked a specific SBP: androgen binding in this species is apparently limited to albumin and CBG.

Photoperiod-induced differences in uterine growth in Phodopus sungorus are evident at an early age when serum estradiol and uterine estrogen receptor levels are not different

“…In the present study, we also ruled out a LD-SD difference in SHBG concentrations as a possible explanation for the spuriously high E2 concentrations in SD that were reported by van den Hurk et al (2002). The relatively low binding affinity that Siberian hamster SHBG has for E2 (present study, Gustafson et al 1989) and for E1 (Gustafson et al 1989) also argues against SHBG causing high E2 in unextracted serum samples. Alternatively, other substances within the serum could bind non-specifically to the E2 antibody of the RIA, and these yet-to-be-determined substances could be found in higher concentrations in SD than in LD hamsters.…”

Characterization and developmental expression patterns of testicular androgen-binding protein in the Djungarian hamster (Phodopus sungorus)

“…Similar patterns have been observed in pubertal monkeys and rabbits (Weddington et al, 1974;Berger et al, 1980;Forest et al, 1986;Westphal, 1986a, b;Keeping et al, 1990). Although other rodents also upregulate ABP at puberty, they do not exhibit the postnatal surge in hepatic SHBG expression observed in Djungarian hamsters (Weddington et al, 1974;Berger et al, 1980;Westphal, 1986b;Keeping et al, 1987;Gustafson et al, 1989;Cates et al, 1995).…”

“…This species is also unique among rodents in expressing SHBG. As in primates, serum SHBG concentrations in both male and female hamsters increase markedly after birth and decrease at puberty (Gustafson et al, 1989;Cates et al, 1995). We have previously characterized SHBG in this species and observed age-related changes in SHBG glycosylation patterns (Cates et al, 1995).…”

“…Similar developmental patterns of ABP and SHBG expression have been observed in rabbits (Weddington et al, 1974;Berger et al, 1980;Westphal, 1986a, b). Unlike primates and rabbits, most rodent species (including rats, mice and golden hamsters) do not express SHBG after birth (Westphal, 1986a; Gustafson et al, 1989;Sullivan et al, 1991;Joseph, 1994). As in other species examined, ABP expression is upregulated during puberty in rats; however, the testicular concentration of ABP varies greatly from species to species (Carreau, 1986;Forest et al, 1986;Westphal, 1986b;Joseph, 1994).…”