Changes of the activities of enzymes involved in prostaglandin synthesis in rat skin during development and aging.

The developmental changes of enzymes involved in prostaglandin (PG) synthesis were investigated in rat skin from birth to 1.5 years old. In all stages of development, the activities of PG-synthesizing enzymes were found in 100,000 x g supernatants of homogenates of rat skin, and PGD2 was the major PG among those formed from PGH2 in the presence of 1 m zeta glutathione (GSH). The PGD synthetase activity in rat skin at birth was 2.14 nmol/min per mg protein, increasing to the highest level (3.69 nmol/min per mg protein) at 3 weeks after birth and then gradually decreasing up to 1.5 years old. The activities of PGE2 and PGF2 alpha synthetases in rat skin were almost unchanged during development and aging. In contrast, the activity of GSH-S-transferase was at its lowest level at birth and gradually increased, reaching a plateau at 3 weeks after birth and remaining relatively constant during the development. The increase of PGD synthetase activity in 3-week-old rats was mainly due to the increase of specific activity of PGD synthetase in the epidermis, which was separated from the dermis by heat treatment (55 degrees C, 30 s). Immunohistochemical study, using (rat spleen PGD synthetase)-specific antibody, revealed that the number of immunopositive cells, which were identified as Langerhans cells, increased in the epidermis in 3-week-old rats. These results suggest that a change of PGD2 synthetase activity during aging of the skin is closely related to the development of ATPase+ Langerhans cells in the epidermis.