Molecular and morphological analysis on the mechanism of regulation by steroid synthesis in lymphoid tissues.

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Concerning the ability of steroid synthesis in the rat abdominal organs, we already reported that the parietal cells in the rat stomach secrete estrogens into the portal vessels. We hypothesized that there is a species difference in the steroid synthesis in the abdominal organs and in mammals including the primates the lymphoid tissues including spleen can synthesize estrogens and the synthesized steroids make some regulations in the lymphoid tissues or through the relation between the lymphoid tissues and the liver. Therefore we examined immunohistochemically the expression of some steroid metabolizing enzymes including aromatase in the lymphoid tissues, which contained thymus, spleen, lymph nodes and Payer's patches of ileum, of rats during postnatal development. We used the following antibodies against aromatase, 5α-reductase type 1, 2, 3α-hydroxysteroid dehydrogenase, 3β-hydroxysteroid dehydrogenase, cholesterol side-chain cleavage enzyme and so on. These steroid metabolizing enzymes were expressed in the lymphocytes, macrophages, dendritic cells, epithelial reticular cells after the early postnatal period onwards. The cellular pattern of the expression was characteristic of each enzyme.