Arachidonic acid metabolism in guinea pig skin

Studies were conducted to examine the metabolism of radioactively labelled arachidonic acid via the lipoxygenase and cyclooxygenase pathways and the metabolic conversions of radioactively labelled prostaglandin H2 in the epidermal and dermal layers of the guinea-pig skin. Arachidonic acid was metabolized preferentially via lipoxygenase to hydroxyeicosatetraenoic acid (HETE). The major product of the cyclooxygenase pathway was prostaglandin D2; prostaglandin E2 was formed in lesser amounts. Epidermis exhibited much higher activities of these enzymes on a milligram protein basis than the dermis. In contrast, both skin layers showed the same very high activity of GSH-dependent prostaglandin H2/prostaglandin D2 isomerase; Prostaglandin D2 was virtually the only product formed by skin homogenates from prostaglandin H2. Guinea-pig skin is a highly active site of arachidonic acid metabolism. These findings will provide the basis for pathobiochemical studies in inflammatory and hyperproliferative dermatoses.