Variations in hepatic metallothionen, zinc and copper levels during an annual reproductive cycle in rainbow trout,Salmo gairdneri.

The normal variations in hepatic levels of metallothionein, zinc and copper were studied during an annual reproductive cycle in rainbow trout of both sexes. In female fish, the total hepatic zinc levels closely followed the estradiol-17β and the LSI levels. Hence, the zinc levels rose in September, peaked in December and dropped in January. No distinct peaks were, however, observed in the whole-liver copper content. The hepatic metallothionein levels in female fish began to increase at the onset of exogenous vitellogenesis. Maximum levels were reached after estradiol-17β and LSI levels had dropped in January. In male fish no distinct peaks in either zinc or copper levels were observed. The metallothionein levels increased somewhat during the time of spermatogenesis. It is suggested that metallothionein may regulate the hepatic zinc distribution during the annual reproductive cycle in female rainbow trout, thereby ensuring the organism of a control mechanism to keep the pool of available zinc at an appropriate level.