The unknown biochemical role of
arginase in epidermal metabolism was probed by examining the association of elevated
arginase activity with epidermal
hyperplasia and hyperkeratinization. Epidermal
hyperplasia was induced experimentally by topical application of
1-decanol to the right side of male hairless mice while the contralateral side served as control.
Arginase activity, incorporation of 3H-thymidine into
DNA,
DNA and
protein content were measured in the separated control and experimental epidermis six hours and on days 1 through 5 and 7 after
1-decanol application. After six hours, the epidermis appears damaged histologically, and
DNA synthesis is inhibited. By day 1, incorporation of 3H-thymidine into
DNA is elevated and a new hyperplastic epidermis has formed beneath the original epidermis. Epidermal
arginase is elevated two through seven days after
1-decanol application and always is associated with continuing epidermal
hyperplasia. The stimulation of
DNA synthesis, which parallels the induction of epidermal
hyperplasia by
1-decanol, precedes the induction of epidermal
arginase activity. An attempt to relate these results with
polyamine synthesis and other metabolic events is made.