Effect of 17α-methyl testosterone incorporated diets on growth of spotted snakehead, Channa punctatus and white carp, Cirrhinus mrigala

The effect of different concentrations of 17α-methyl testosterone incorporated diet on growth performance in the fry of Channa punctatus and Cirrhinus mrigala was evaluated. Four different doses of hormone such as 60, 80, 100 and 120 mg/kg in C. punctatus and 40, 60, 80 and 100 mg/kg in C. mrigala were administered through diet for a period of 90 days.

Fifth group on a hormone free diet served as a control. The growth performance in terms of length and weight gain of the fry receiving 100 mg/kg in C. punctatus and 60 mg/kg in C. mrigala were significantly higher than those receiving 80, 120 and 0 (untreated control) mg hormone per kg feed. The highest specific growth rate (0.864 ± 1.18%WG d⁻¹) at 100 mg/Kg diet and (2.47 ± 1.26%WG d⁻¹) at 60 mg/kg diet were observed in C. punctatus and C. mrigala respectively, showing positive influence of hormone incorporated diet on the growth performance. However, the survival rate of both the species remained unaffected by different dosages of 17α-methyl testosterone.

An in vitro model for evaluating peripheral regulation of growth in fish: effects of 17β-estradiol and testosterone on the expression of growth hormone receptors, insulin-like growth factors, and insulin-like growth factor type 1 receptors in rainbow trout (Oncorhynchus mykiss)

A central component of growth coordination in vertebrates is the growth hormone (GH)-insulin-like growth factor-1 (IGF-1) system. To date, most studies on the control of vertebrate growth have focused on regulation of pituitary GH production and release. In this study, we used liver, muscle, and gill tissue from sexually immature rainbow trout incubated in vitro to evaluate the extrapituitary effects of 17β-estradiol (E2) and testosterone (T) on mRNA and functional expression of growth hormone receptors (GHR), insulin-like growth factors 1 and 2 (IGF-1, IGF-2), and type 1 IGF receptors (IGFR1). E2 significantly decreased steady-state levels of GHR1, GHR2, and IGF-1 mRNAs in liver as well as of GHR1 and GHR2 mRNAs in muscle and of IGF-1 and IGF-2 mRNAs in gill in a time- and concentration-dependent manner. E2 had no effect on levels of IGFR1 mRNAs in muscle or on GHR and IGFR1 mRNAs in gill. Functional expression of GHRs as assessed by (125)I-GH binding capacity was reduced by E2 in liver and muscle; however, E2 did not affect (125)I-IGF-1 binding capacity in muscle or (125)I-GH and (125)I-IGF-1 binding capacity in gill. By contrast, T increased steady-state levels of GHR1, GHR2, IGF-1, and IGF-2 mRNAs in liver, of GHR1, GHR2, IGFR1A, and IGFR1B in muscle, and of GHR1, GHR2, IGF-1, IGF-2, IGFR1A, and IGFR1B mRNAs in gill in a time- and concentration-dependent manner. Binding capacity of (125)I-GH in liver and of (125)I-GH and (125)I-IGF-1 in both muscle and gill also was increased by T. These data indicate that E2 and T directly affect peripheral aspects of the GH-IGF system, and suggest, at least in immature rainbow trout, that E2 reduces hepatic sensitivity to GH as well as reduces peripheral production of IGFs and that T increases peripheral sensitivity to GH and IGF as well as increases peripheral production of IGFs.

The effects of 11-ketotestosterone and testosterone on the skin structure of brown trout, Salmo trutta L

11-Ketotestosterone and testosterone were administered by intraperitoneal implants to immature brown trout. Physiological levels of circulating androgens were maintained over a period of 4 months and this resulted in changes in skin structure which resembled those occurring in maturing male brown trout. 11-Ketotestosterone promoted both epidermal and dermal thickening, and markedly reduced the number of superficial goblet cells, whereas testosterone stimulated only epidermal thickening. The relative roles of these two androgens in the normal maturational processes of brown trout are discussed.

Influence of testosterone on precocious sexual development in immature rainbow trout

The influence of testosterone on plasma and pituitary levels of gonadotrophin (GTH) as well as on gonadal development was studied in immature rainbow trout. Among the animals receiving a testosterone-cocoa butter implant (200 micrograms) at the age of 5 months, gonadal puberty occurred 8 months later in half of the males (opposite to the controls which remained immature) and the beginning of oocyte maturation was observed in only one female. These animals were characterized by a higher pituitary GTH level. Owing to the multivariate statistical analyses made, it was possible to provide evidence for the presence of two populations with different reactions to the same steroid treatment. They also confirmed the existence of a positive testosterone feedback, in the male, leading to a precocious gonadal development. The pituitary GTH load obtained with 200 micrograms of testosterone seemed to be related to the age of first maturation. The secretion of an appropriate level of GTH resulting in the stimulation of gametogenesis required the availability of a relatively large pituitary GTH level and seemed to be possible because the animals were already in the pubertal period. The fact that the highest pituitary GTH level of the treated lot was found in the only female showing a beginning of sexual maturation suggests that testosterone may also act in females.