The role of sex steroids in the formation of sex-differentiated concentrations of corticosteroid-binding globulin in rats

Abstract

The role of sex steroids in the programming of the level of serum corticosteroid-binding globulin (CBG) in the rat has been studied at different stages of ontogenesis. The CBG content in the serum of mature female rats was 2.5 times higher than that in male rats. Sexual dimorphism of CBG content was absent in immature animals of 3-4 weeks of age. Castration of mature rats led to a 40-50% increase in CBG content. The CBG concentration in mature females or castrated adult males treated with testosterone propionate (TP; 3 mg/day for 4 days) was decreased by 40-50% compared with vehicle-treated rats. Oestradiol injection (1 microgram/day for 4 days) had no influence on CBG levels in mature male and ovariectomized adult female rats. Immature rats were castrated on days 1, 7, 14, 21, 28 or 35 of age and the CBG level was determined at 10-12 weeks of age. The CBG content of rats castrated up to day 28 of age was 2.5 times higher than that in mature males and did not differ from that in mature females. The CBG content of male rats castrated on day 35 of age was the same as that of adult castrated males. The CBG level in castrated rats treated with TP (1.25 mg for days 1-3 or 300 micrograms/day for 5 days after castration at day 7 up to day 26) did not differ from that in controls (i.e. vehicle-treated rats).(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian Variation in Basal Plasma Corticosterone and Adrenocorticotropin in the Rat: Sexual Dimorphism and Changes across the Estrous Cycle*

“…This is consistent with the observation that sexual dimorphism in CBG levels of the rat primarily reflects the masculinizing effect of androgens during development in males, rather than any sensitivity of CBG to estrogen in adult females (27). Indeed, even ovariectomy in the adult female rat has no demonstrable effect on the level of plasma CBG (27).…”

“…Changes in plasma corticosterone during the estrous cycle are also unlikely to reflect shifts in CBG levels, as the proportion of total plasma corticosterone that is unbound appears stable across the cycle (11). This is consistent with the observation that sexual dimorphism in CBG levels of the rat primarily reflects the masculinizing effect of androgens during development in males, rather than any sensitivity of CBG to estrogen in adult females (27). Indeed, even ovariectomy in the adult female rat has no demonstrable effect on the level of plasma CBG (27).…”

Gender differences in response of hippocampus to chronic glucocorticoid stress: Role of glutamate receptors

“…CGB appears to buffer plasma corticoids and reduce their availability to cells. CGB levels are higher in female than in male rats (Mataradze et al, 1992;Galea et al, 1997). Higher CGB may result in retention of corticosteronein plasma, resulting in higher values in female.…”

“…First, CBG levels in rats are 2.5-fold higher in females than in males (Mataradze et al, 1992;Galea et al, 1997). Second, relative levels and occupancy of mineralcorticoid (MCr) and glucocorticoid (GCr) receptors in hippocampus differ between males and females (Turner, 1992).…”

Peripheral and Central Sex Steroids Have Differential Effects on the HPA Axis of Male and Female Rats

“…This is consistent with evidence that the CBG levels may be sexually differentiated by androgen exposure early in development. Androgen treatment was less effective at lowering CBG levels in adult males gonadectomized as neonates than males gonadectomized as juveniles or as adults (Jansson et al, 1989;Mataradze et al, 1992;McCormick et al, 1998a). The pattern of sex hormone effects on CBG levels and pattern of effects on post-stress corticosterone levels are different.…”