The catabolism of prostaglandins by rat skin

The activities of NAD+-dependent 15-hydroxy prostaglandin dehydrogenase in soluble fractions of rat skin and lung were compared by using a radiochemical assay method. Tritiated prostaglandin F2 alpha was incubated with NAD+ and 120,000 g supernatant of tissue homogenate. Extracted prostaglandin substrate and reaction products were separated by t.l.c. and quantitatively determined by liquid-scintillation counting. With skin 120,000 g supernatant, 10 mM-NAD+ and an incubation time of 15 min, the mean Vmax. was 5.5 nmol of prostaglandin F2 alpha converted/s per litre of reaction mixture. With lung 120,000 g supernatant, 60 mM-NAD+ and an incubation time of 5 min, the mean Vmax. was 26.9 nmol/s per litre, demonstrating 5-fold greater dehydrogenase activity in lung per unit wet weight of tissue. However, the total wet weight of skin was about 23 times that of lung, on dissection of individual rats, indicating that the entire skin may contain 4.5 times the total 15-hydroxy prostaglandin dehydrogenase activity of the lungs. Skin may thus be an important organ of prostaglandin catabolism.