Effects of cadmium and zinc on steroid metabolism and steroid level in the sea star Asterias rubens L.

Steroid metabolism was studied in gonads and pyloric caeca of male and female sea stars which had been exposed to cadmium or zinc for 3 weeks. Steroid metabolism had increased in animals exposed to heavy metals. Significant increase of the enzyme activity was observed for 17 alpha-hydroxylase in the pyloric caeca of female animals exposed to zinc (pregnenolone----17 alpha-hydroxypregnenolone) or cadmium (progesterone----17 alpha-hydroxyprogesterone), for 17 beta-hydroxysteroiddehydrogenase in the gonads of female animals (dehydroepiandrosterone----androstenediol) and in pyloric caeca of male animals (androstenedione----testosterone) after exposure to cadmium, and for 5 alpha-reductase (progesterone----5 alpha-pregnane-3,20-dione) in ovaries of cadmium exposed sea star. There is some evidence that pregnenolone metabolism in male and female animals is affected by zinc in a different way. The effect of cadmium on the esterification of androstenedione differed highly significantly among male and female animals. It was concluded that the main way of entrance of cadmium into sea stars is via the surrounding medium and not via the food consumed. Testosterone and progesterone levels in, respectively, gonads of female and pyloric caeca of male sea stars which had been exposed to cadmium were significantly higher than the corresponding values in control animals. The effect of zinc exposure on testosterone level in pyloric caeca is significantly different for both sexes. Cadmium interacts directly with the esterification of testosterone, strongly stimulating this process. Cadmium stimulates the production of testosterone by action at the level of the biosynthesis of 17 beta-hydroxysteroiddehydrogenase.