Estradiol-17β effects on lipid and carbohydrate metabolism and on the induction of a yolk precursor in goldfish,

The effects of estradiol-17β treatment on plasma lipid levels, liver lipid and glycogen reserves were examined during different phases of the reproductive cycle in goldfish, . Estrogen therapy resulted in increased plasma and hepatic lipid levels except during the spawning season. Hepatic glycogen deposits were depleted by estradiol injections during all seasons. Treatment of fish with the estrogen antagonist, CI-628, during the spawning season caused a reduction in plasma and liver lipid levels. Electrophoretic studies conducted during the post-spawning season showed that estrogen induces the appearance of a specific lipoprotein, probably a yolk precursor, in the serum and liver of goldfish.     

Diurnal variations in the physiology of the goldfish,Carassius auratus

Abstract

Liver glycogen, liver lipid, liver triglycerides, plasma glucose, plasma total lipid, plasma cholesterol, plasma corticoids, hypothalamic serotonin and pituitary pro‐lactin levels were assayed at five times over a 24‐h period in Carassius auratus maintained under a specific photoperiod regime at various times throughout the year. Diurnal variations were observed in all parameters monitored. Daily variations of liver glycogen, plasma glucose, plasma lipid, plasma corticoids and hypothalamic serotonin were affected by time of feeding. Liver glycogen, plasma lipid and plasma corticoid levels were also affected by time of feeding. Diurnal variations of liver glycogen, plasma glucose and plasma lipid were influenced by light‐dark cycles. These data illustrate that feeding time, photoperiod and time of sacrifice are important considerations in the study of metabolic and hormonal parameters in fishes.     

The effect of monooxygenase inducing agents on the incorporation of [35S]methionine into hepatic microsomal protein of rainbow trout (Salmo gairdneri)

Treatment of rainbow trout (Salmo gairdneri) with 150 mg/kg BNF resulted in an increase in hepatic microsomal monooxygenase activity as assessed by ECOD and EROD when compared to those activities in corn oil-pretreated animals. Administration of 100 mg/kg 2,4,5,2',4',5'-hexachlorobiphenyl (6-CB) to trout had no significant effect on these catalytic activities or on BeND. The amount of radioactivity in hepatic microsomes at 24, 48 or 72 hr following the administration of 75 muCi of [35S]methionine was consistently higher in animals pretreated with BNF than in those treated with corn oil or 6-CB. Autoradiography/fluorography of electrophoretograms demonstrated the appearance of at least three radiolabeled bands in the 50,000-60,000 mol. wt range in solubilized microsomes from BNF-treated fish which were not present in microsomes from control animals or fish treated with 6-CB. These data indicate that the stimulation of hepatic microsomal catalytic activities observed following the administration of 3-MC-type agents to rainbow trout is due, at least in part, to induction of enzyme(s) rather than activation of existing enzyme(s). These results further support the observation that fish appear to be non-responsive to phenobarbital-type inducing agents.     

Induction in rainbow trout of an acute phase (C-reactive) protein by chemicals of environmental concern

1. Rainbow trout, Salmo gairdneri, produce elevated amounts of a serum acute phase (C-reactive) protein (CRP) when administered a variety of chemicals of environmental importance. 2. Compounds administered in doses which induce the cytochrome(s) P450 catalytic enzymes in trout hepatic microsomes also induce serum CRP. 3. However, an interferon-inducing virus does not induce CRP. Interferon induction by the virus is not significantly inhibited by chemicals which induce trout cytochrome(s) P450. 4. Simultaneous administration of chemicals and virus or virus alone results in depression of P450 protein production and only minor induction of CRP. 5. Thus, as with mammals, a reciprocating relationship appears to exist between the hemeprotein monooxygenase and immune systems of this freshwater teleost, and C-reactive protein appears to fit the reciprocating scheme closer to the cytochromes P450 response.     

The effects of blinding,pinealectomy and exposure to constant dark conditions on gonadal activity in the female goldfish,Carassius auratus

Synopsis The effects of pinealectomy, blinding, and exposure to constant darkness were examined in female goldfish during different seasons. Neither blinding nor pinealectomy under short or decreasing photoperiod conditions, nor exposure to constant darkness had an effect on ovarian activity in goldfish during fall and winter. In spring, constant darkness has an inhibitory effect on ovarian activity. Pinealectomy under increasing photoperiod conditions partially inhibits reproductive activity, but not to the extent of constant darkness. Blinding, under the same regime also inhibited to some extent the ovarian response to increasing photoperiod. Our data suggest that retinal pathways and the pineal organ are involved in the photosexual response to increasing day lengths.Address correspondence to: Dr. V. L. de Vlaming, Marquette University     

The effect of sex steroids and pregnenolone-16 alpha-carbonitrile on the hepatic microsomal monooxygenase system of rainbow trout (Salmo gairdneri)

Estradiol benzoate (EB-5 mg/kg) or testosterone propionate (TP-50 mg/kg) administration to sexually immature rainbow trout resulted in an increase in liver weight to body weight ratios, and a diminution in hepatic microsomal benzphetamine-N-demethylation (BeND), ethoxycoumarin- and ethoxyresorufin-O-deethylations (ECOD, EROD) and cytochrome(s) P-450 content when compared to corn oil-pretreated controls. A low dose of TP (2 mg/kg) caused an increase in cytochrome(s) P-450 content but had no effect on the selected monooxygenase activities. EB administration prior to treatment with 150 mg/kg beta-naphthoflavone caused a dose-dependent decrease in the magnitude of induction of cytochrome(s) P-450 and associated catalytic activities. These data suggest that the sex differences in monooxygenation observed in prespawning trout are mediated via the sex steroids and that fish may respond differently to inducers depending on their reproductive state at the time of exposure. Administration of the synthetic steroid, pregnenolone-16 alpha-carbonitrile (PCN), resulted in an increase in BeND and ECOD but had no effect on EROD or cytochrome(s) P-450 content.     

Does pinealectomy,anopsia or exposure to constant darkness affect pituitary prolactin levels in the goldfish,Carassius auratus L.?

Synopsis The ef fects of exposure to constant darkness, anopsia and pinealectomy on pituitary prolactin levels in the goldfish were examined. Determination of prolactin was made in a polyacrylamide microelectrophoretic system coupled with densitometry. Neither pinealectomy nor anopsia had an effect on pituitary prolactin content in the fall. Exposure to constant darkness in the fall was without obvious effect, whereas such treatment in the spring resulted in significantly elevated pituitary prolactin content. Pinealectomy in the spring did not alter pituitary content, suggesting that the response to constant darkness is independent of the pineal organ, perhaps involving retinal or extra-retinal photoreception.     

The effects of pinealectomy on pituitary and plasma gonadotropin levels in Carassius auratus exposed to various photoperiod–temperature regimes

The effects of pinealectomy on pituitary and plasma gonadotropin levels and gonadal development in female goldfish exposed to various photoperiod-temperature regimes during different seasons were examined. Pinealectomy during autumn had no effect on either pituitary or plasma hormone levels or gonadal development. When goldfish are pinealectomized in spring and exposed to long photoperiod conditions, the ovaries regress and plasma gonadotropin levels are significantly depressed compared to sham operated animals. Sham operated goldfish exposed to short photoperiod conditions in spring had regressing ovaries whereas pinealectomized animals under this regime either spawned or had ovaries in the late vitellogenic phase. Plasma gonadotropin titres in the pinealectomized group were significantly lower than those of sham operated animals. The pineal can be either stimulatory or inhibitory to gonadal development depending on the photoperiod regime to which the animals are exposed. The pineal apparently influences gonadal activity by modulating gonadotropin secretion. A diurnal variation in plasma gonadotropin levels was also observed in both sham operated and pinealectomized goldfish exposed to a long photoperiod warm-temperature regime in spring.     

Estradiol-17β effects on lipid and carbohydrate metabolism and on the induction of a yolk precursor in goldfish, CarassiusAuratus

The effects of estradiol-17β treatment on plasma lipid levels, liver lipid and glycogen reserves were examined during different phases of the reproductive cycle in goldfish, $\text{Carassius}$$\text{auratus}$. Estrogen therapy resulted in increased plasma and hepatic lipid levels except during the spawning season. Hepatic glycogen deposits were depleted by estradiol injections during all seasons. Treatment of fish with the estrogen antagonist, CI-628, during the spawning season caused a reduction in plasma and liver lipid levels. Electrophoretic studies conducted during the post-spawning season showed that estrogen induces the appearance of a specific lipoprotein, probably a yolk precursor, in the serum and liver of goldfish.     

Effects of pinealectomy on pituitary gonadotrophs, pituitary gonadotropin potency and hypothalamic gonadotropin releasing activity in Notemigonus crysoleucas

The effects of pinealectomy on pituitary gonadotrophs, pituitary gonadotropin potency and hypothalamic gonadotropin releasing activity were examined in the cyprinid teleost, Notemigonus crysoleucas, exposed to various photoperiod-temperature regimes. In fish exposed to a long photoperiod-warm temperature regime, pinealectomy resulted in a decrease in gonadal activity, in hypothalamic gonadotropin releasing activity and an increase in pituitary gonadotropin potency. Fewer gonadotrophs were present in the pituitary of sham operated fish than in the pituitary of pinealectomized fish. Ovarian development was more rapid in sham operated than in pinealectomized fish exposed to a long photoperiod–low temperature regime. Pituitary gonadotropin activity was also greater in shams than in pinealectomized fish. A short photoperiod-warm temperature regime retarded ovarian development in N. crysoleucas. Pinealectomy reversed this trend. Gonadotrophs made up a greater area of the pituitary in pinealectomized fish than in shams under these conditions. Gonadotropin potency of the pituitary and hypothalamic gonadotropin releasing activity were also greater in pinealectomized fish than in shams. The area of the pituitary occupied by gonadotrophs was greater in pinealectomized than in sham operated animals maintained on a short photoperiod-low temperature regime. Pituitary gonadotropin activity was also greater in pinealectomized fish as compared to shams. Pituitary gonadotropin potency varies diurnally in animals maintained on both short and long photoperiods; the rhythm of variation differs depending on photoperiod. Pinealectomy alters the diurnal rhythm of pituitary gonadotropin potency in animals exposed to both long and short photoperiods. It is concluded that pinealectomy has a pronounced effect on reproductive activity in N. crysoleucas. The effects of pinealectomy on reproduction vary with photoperiod, but are mediated via the hypothalamus and pituitary. In fish exposed to long daylengths the pineal favours reproductive activity, but the epiphysis retards reproductive processes in animals maintained on short photoperiods.