Effect of 17α-methyltestosterone, estradiol-17β and synthetic LHRH on production of gonadotropic hormone in pituitaries of rainbow trout (organ culture)

Abstract

Pituitary glands from 6-month-old sexually immature female rainbow trout, Salmo gairdneri, were kept in organ culture for 48 or 72 h. Certain groups of pituitaries were cultivated for 48 h on either control medium or medium with 17 alpha-methyltestosterone (MT), or with estradiol-17 beta (E2) in concentrations of 8.5 X 10(-7) M. Other groups of pituitaries were cultivated for 72 h on control medium, or for 48 h on either control medium or MT-medium or E2-medium, and subsequently for 24 h on medium with synthetic LHRH in concentrations of 8.5 X 10(-7) M and 8.5 X 10(-10) M. Gonadotropic (GTH) cells are identified by Alcian Blue-Periodic Acid Schiff-Orange G staining and the double-antibody immunoenzyme-cytochemical technique using anti-carp beta GTH as the first antibody. A quantitative histological procedure was used to study the nuclear size of the GTH cells in response to the different hormones. Secretory activity was estimated by measuring the gonadotropin (GTH) content in extracts of pituitaries, plasma, and the culture media every 24 h by radioimmunoassay. Cultivation on MT- or E2-enriched medium results in an increase of the total amount of GTH in the pituitary and medium, an accumulation of GTH in GTH-cells (approximately 20 percentage points) and an increase in their nuclear size, indicating a stimulation of GTH synthesis. However, autonomous GTH-release is not affected by these steroids. Subsequent cultivation of the pituitaries for 24 h with LHRH causes stimulation of GTH synthesis (approximately 20 percentage points). Preincubation with steroids increases the GTH synthesis capacity of LHRH only when used in a concentration of 8.5 X 10(-10) M. Moreover, 8.5 X 10(-7) M LHRH causes a stimulation of GTH-release. Preincubation of the pituitaries with steroids increases the responsiveness of GTH-cells to LHRH. It is concluded that GTH-production in pituitaries of immature female rainbow trout can be directly influenced by gonadal steroids and by a hypophysiotropic substance.

Aromatase activity in brain and pituitary of immature and mature atlantic salmon (Salmo salar L.) parr

“…Ikuta et al (1987) found the same stimulatory effect of high doses of testosterone and the nonaromatizable 11-ketotestosterone on pituitary GTH content in immature masu salmon, Oncorhynchus masou. The positive effect of androgen on GTH accumulation in young rainbow trout is due to a stimulation on the pituitary level (Fahraeus-van Ree et al, 1983;Gielen and Goos, 1983). Prolonged treatments also lead to elevated GTH levels in the plasma (Crim and Evans, 1983).…”

Gonadotropins I and II in juvenile coho salmon

“…In most cases, gonadotropin-releasing hormone (GnRH) was required to stimulate secretion of the stored hormone (c.f. Gielen and Goos 1983;Fahraeus-van Ree et al 1983). Therefore, the hypothalamic-pituitary-gonad (HPG) axis is operational in immature trout.…”

In vitroInduction of Luteinizing Hormone Synthesis by Estrogen in Organ-Cultured Pituitary Glands of the Japanese Eel, Anguilla japonica

“…This seems also to be the case in some teleosts such as the rainbow trout (Fåhraeus-van Ree et al ., 1983) and goldfish (Huggard et al ., 1996). In the present study, we developed an organ culture method for the pituitary gland isolated from the Japanese eel, Anguilla japonica , and examined the in vitro effect of E2 on the synthesis of a GTH subunit, LH β .…”

“…These sex steroids stimulate GTH production in organ-cultured pituitary glands of the rainbow trout and goldfish (Fåhraeus-van Ree et al ., 1983;Huggard et al ., 1996). Similarly, GTH production in primary culture of eel pituitary cells is stimulated by testosterone and some other steroids, but unexpectedly not by E2 (Huang et al ., 1997).…”

“…Such stimulatory effects of sex steroids are attributable, at least in part, to a direct action on the pituitary gland. In fact, many in vitro studies have shown that sex steroids directly stimulate LH expression in cultured pituitary glands and/or cells of juvenile rainbow trout (Fåhraeus-van Ree et al ., 1983;Xiong et al ., 1994), immature and mature goldfish (Huggard et al ., 1996), and maturing tilapias (Melamed et al ., 1998).…”