The cytochrome P450 system of Atlantic salmon (Salmo salar): II. Variations in hepatic catalytic activities and isozyme patterns during an annual reproductive cycle

Pellets designed for continuous, long-term, oligopeptide, hormone delivery were implanted into the adult landlocked Atlantic salmon (Salmo salar) to investigate the effects of LHRH agonist analogue (LHRH-A) upon the reproductive system. Chronic elevations in plasma gonadotropin were observed in experimental fish at a variety of stages of reproductive development. Synthesis of pituitary gonadotropin was also evoked in sexually regressed fish and fish undergoing gonadal recrudescence, but the already elevated level of pituitary GtH observed in prespawning and spawning salmon was not augmented. In prespawning fish, the events of ovulation and spermiation were accelerated by LHRH-A treatment. The LHRH-A hormone treatment also increased milt volume and the duration of spermiation in ripe males. In sexually regressed males LHRH-A treatment did not induce the advanced phases of spermatogenesis but some testicular stimulation was indicated by the presence of increased numbers of B-type spermatogonia and enlargement of the lumen of lobules. The gonadal response to LHRH-A treatment during the rapid phase of gonad recrudescence differed in males and females. Based upon the changes in GSI, the LHRH analogue accelerated vitellogenic development of the ovaries in females; in males, however, the GSI was significantly reduced following LHRH-A administration. Whereas, it seems clear that a long acting preparation containing LHRH-A can be successfully used in prespawning fishes to advance the final events of gonadal maturation and initiate spawning, further studies are necessary to evaluate the potential of LHRH agonists to either stimulate or inhibit the reproductive development of fish at other stages of the seasonal reproductive cycle.Key words: fish, teleosts, landlocked salmon, LHRH analogues, gonadotropic hormone releasing hormones, seasonal reproductive cycle, gonad development, spawning

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Steroid hormone levels and patterns of growth in the early part of the reproductive cycle of adult Atlantic salmon (Salmo salar L.)

Aquaculture ◽

10.1016/0044-8486(88)90193-7 ◽

1988 ◽

Vol 69 (1-2) ◽

pp. 145-157 ◽

Cited By ~ 25

Author(s):

A.F. Youngson ◽

H.A. McLay ◽

R.S. Wright ◽

R. Johnstone

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Reproductive Cycle ◽

Steroid Hormone ◽

Hormone Levels ◽

Atlantic Salmon Salmo Salar

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Effects of Dietary Iron Concentrations on the Cytochrome P450 System of Atlantic Salmon (Salmo salar)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f94-032 ◽

1994 ◽

Vol 51 (2) ◽

pp. 315-320 ◽

Cited By ~ 14

Author(s):

Anders Goksøyr ◽

Marit Bjørnevik ◽

Amund Maage

Keyword(s):

Cytochrome P450 ◽

Atlantic Salmon ◽

Salmo Salar ◽

Dietary Iron ◽

Iron Group ◽

Cytochrome P450 1A1 ◽

Potent Inducer ◽

Monooxygenase Activity ◽

High Iron ◽

Atlantic Salmon Salmo Salar

Groups of Atlantic salmon (Salmo salar) parr were fed a basal diet containing 27 mg Fe∙kg feed−1 supplemented with different iron levels (0, 80, and 160 mg∙kg−1, respectively) for 8 wk. After this period, a subgroup of each iron regime was treated intraperitoneally with β-naphthoflavone (BNF), a potent inducer of cytochrome P450 1A1 in fish. Differences between the iron regimes were observed in hepatic iron content, which was higher in the high-iron group, and in P450 1A1 levels and monooxygenase activity, measured as 7-ethoxyresorufin O-deethylase (EROD), which were lower in the high-iron group. Differences were also observed in the induction response of P450 1A1 and EROD to BNF. Levels of a constitutive isozyme denoted P450con, belonging to the P450 3A subfamily, did not respond to the dietary iron in the same manner, demonstrating selective regulatory effects of iron on different P450 isozymes.

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