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The insulin like growth factors I and II are the most ubiquitous in the mammalian embryo. Moreover they play a pivotal role in the development and growth of tumours. The bioavailability of these growth factors is regulated on a transcriptional as well as on a posttranslational level. The expression of non-signalling receptors as well as binding proteins does further tune the local concentration of IGFs. This paper aims at reviewing how the transcription of the IGF genes is regulated. The biological significance of these control mechanisms will be discussed.

Morphological studies of gonads from roach (Rutilus rutilus) in a small Swedish lake were performed. The lake is a potential recipient for drainage water from a refuse dumping area. All fishes were macroscopically identified as males, but histological examination of the gonads showed a high incidence of intersex. This high incidence might be caused by endocrine disrupting chemicals. The relationships between exposure to endocrine disrupters and intersex observations in wild fish is unknown and the effect of endocrine disrupters on zebrafish (Danio rerio) were evaluated in order to determine whether they might serve as a model laboratory species for effects of endocrine disrupting chemicals in wild fish. Zebrafish were exposed from pre-blastula stage until sexual maturation to either standardised water (controls), 17a-methyltestosterone (1, 10 μg l-1) or 17b-estradiol (1, 10 μg l-1). Exposure to both concentrations of 17bestradiol caused a significant feminisation, while a significant increase in the proportions of males was found after exposure to 1 mg 17a-methyltestosterone l-1. Furthermore, exposure to 1 and 10 mg 17a-methyltestosterone l-1 caused development of intersex individuals. Additionally, sexually mature male zebrafish were exposed to 1 μg 17b-estradiol l-1. After 10 weeks of exposure the fish were transferred to non-contaminated water for two weeks. The control group was kept in standardised water for 12 weeks. At termination of the experiment, measurement of whole-body vitellogenin concentrations were performed. Exposure to 17b-estradiol caused a significant increase in whole body vitellogenin concentrations. After 2 weeks in water without addition of 17b-estradiol, the vitellogenin concentration was reduced by approximately 50%. Roach and zebrafish may share properties which makes these species suitable for further comparisons to evaluate effects of endocrine disrupting chemicals as well as domestic and industrial effluents containing hormone-like substances.

Aim-To study how polychlorinated biphenyls (PCBs) aVect fetal growth and the expression of the insulin-like growth factor (IGF II) gene in the mink (Mustela vison). Methods-Ten female mink were each exposed to 0.65 or 1.3 mg Clophen A50/ day, respectively, during the reproductive season. The numbers and sizes of viable fetuses were recorded. The expression of the IGF II gene was studied by northern blotting using a mink specific IGF II cDNA probe. Results-The number of viable fetuses decreased after PCB exposure in a dose dependent fashion. Expression of the IGF II gene in adult livers from PCB exposed animals was decreased, compared with control animals, in a dose dependent fashion. In contrast, IGF II expression in placentas and fetuses was unaltered. Furthermore, the maternal excretion of urinary cortisol increased in both exposed groups during the implantation period. Conclusions-Expression of the IGF II gene is downregulated by PCB exposure in the adult liver. There is also an indication that the regulation of the expression of this gene diVers between adult and fetal life. (J Clin Pathol:Mol Pathol 1998;51:43-47)

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