In vivo and in vitro studies on sex steroid binding protein (SBP) regulation in rainbow trout (oncorhynchus mykiss): Influence of sex steroid hormones and of factors linked to growth and metabolism

Abstract

Summary--The respective roles of sex steroids and hormones related to growth and metabolism, on SBP regulation have been studied in rainbow trout. In vivo, oestradiol (E2) supplementation induces a slow but significant increase of plasma SBP concentration. Testosterone or cortisol injections have no effect. In vitro, the steroid binding protein that accumulates in incubation medium of hepatic cell primary cultures has been characterized and found to be similar to blood SBP. Its production is increased by addition of E2 (maximum: + 300%). This effect develops slowly over several days of culture and is dose dependent; as little as 1-10 nM E2 is effective.Recombinant rainbow trout GH (rtGH)--4).01 to 1 #g/ml--also increases SBP accumulation as compared to control cells and seems to maintain SBP production over culture duration. In preliminary experiments, (1) insulin-like growth factor (IGF) and SBP concentrations were found to change inversely after a 4 days stimulation with increasing concentrations of GH; (2) recombinant human IGF~ (250 ng/ml) tended to be inhibitory when SBP production was expressed per mg of total cellular protein, and a micromolar concentration of bovine insulin was clearly inhibitory.

Effect of 17β-Estradiol and Testosterone Treatment on Sex Steroid Binding Proteins in the Female of the Green Frog Rana esculenta

“…These results are different from those obtained in mammals, where SSBPs are not affected by castration (von Shoultz and Carlstrom, 1989) and androgens seem to play an inhibitory action on SSBP levels in vivo (Toscano et al, 1992;Koritnik and Marschke, 1986;Kottler et al, 1988;). In the only other lower vertebrate studied so far, the trout, androgens do not affect SSBP plasma levels, a result also confirmed by in vitro observations (Foucher et al, 1991). On the contrary, in Rana esculenta testosterone affected EBP binding capacity.…”

“…Since SSBP are believed to be mainly synthesized in the liver (Mercier-Bodard et al, 1989), we can hypothesize a testosterone effect through its aromatization to 17β-estradiol. Indeed, estrogens have been reported to increase SSBP in human, heifer and trout (Toscano et al, 1992;Lermite and Terqui, 1991;Foucher et al, 1991), although they have little or not effect in monkeys (Koritnk and Marschke, 1986;Kottler et al, 1988).…”

Vitellogenin synthesis in cultured hepatocytes; an in vitro test for the estrogenic potency of chemicals

“…Various techniques have been used to culture fish hepatocytes [35,37]. We chose to use the system first developed by Flouriot and Valotaire [38] and modified by Foucher et al [39], in which gentle shaking is used to encourage the hepatocyte to form small aggregates, as a first step towards tissue organization [40]. In our system, the cells are kept for 10 to 12 days (see Fig.…”

Growth hormone (GH) and reproduction: a review

“…In fact, we demonstrated that in trout, in vivo, variations of plasma SBP levels coincided with perturbations of the GH/IGF system (Foucher et al 1992) and that in vitro, recombinant tGH (1-1000 ng/ml) maintained and stimulated SBP production by trout hepatocytes in culture (Foucher et al 1991). Also, GH may exert a selective stimulation of rat liver cytosolic E 2 receptor (Lucier et al 1981;Von Schoultz and Carlstr6m 1989).…”

“…In our hands, GH either alone or in cotreatment with E 2 (10 -7 -10 -6 M) was found to have a slight inhibitory effect on vitellogenin (Vg) accumulation in trout hepatocyte culture medium (Foucher et al 1991) and no effect on Vg mRNA concentration in cultured hepatocytes (Flouriot and Valotaire, unpublished data). However, in vivo, GH was shown to enhance the stimulatory effect of low E 2 doses (0.56 tg/3 times a week/24 days) on Vg plasma levels in female silver eels (Burzawa-Gerard and Delevall6e-Fortier 1992).…”