The effect of 4-nonylphenol on the synthesis of vitellogenin in the flounder Platichthys flesus

Dose-response effects of the putative estrogenic compound 4-nonylphenol (4- NP) on the de novo synthesis of vitellogenin were investigated in the floun der Platichthys flesus. Male flounders received intraperitoneal injections during a period of 2 weeks with 10, 50, 100, 150 and 200 mu g g(-1) week(-1 ) of 4-NP. Controls received the peanut oil vehicle only. The dose-response effects of the treatment were investigated on different plasma indicators of vitellogenin, alkali-labile protein phosphorous, total calcium and prote in. Increased concentrations of these indicated a dose-response induced syn thesis of vitellogenin in the liver of the 4-NP-treated male flounders. Vit ellogenin from plasma of estradiol-treated male flounders was purified by g el filtration followed by ion-exchange chromatography and subsequently subj ected to native gel electrophoresis. The purified vitellogenin fraction app eared as a high molecular protein band of 540 kDa in the electropherograms. The presence of vitellogenin in the plasma of the 4-NP-treated fish could then be directly detected by the native gel electrophoresis method. A high molecular weight vitellogenin band from plasma of the 4-NP-treated males ap peared in the electropherograms in exactly the same position as the purifie d vitellogenin and vitellogenin in plasma of estradiol-treated male Bounder s. No vitellogenin band could be detected in the plasma of control males. T he dose-response effect of the 4-NP-treatment was also reflected by an incr eased thickness of the vitellogenin band of the electropherograms by increa sing doses of the 4-NP. De novo induction of vitellogenin synthesis in the liver was also indicated by increases of the hepatosomatic indices and of h epatic total RNA in the 4-NP-treated fish. No changes could be observed in the hepatic DNA concentrations. A significant increase of plasma GPT-concen trations indicated that 4-NP also elicited toxic effects on the fish. This was further indicated by a high mortality in the group treated with the hig hest dose of 4-NP (200 mu g g(-1)). No effect could be observed on the gona dosomatic indices of the treated fish when compared to the peanut oil-injec ted controls. The present experiments were carried out towards the end of t he reproductive season with testicular size observed to be near maximal in the control group. This is the most likely reason why no effect of the 4-NP injections could be observed on the testicular morphology or growth in the present experiments. (C) 1999 Elsevier Science B.V. All rights reserved.