PERCUTANEOUS EXPOSURE OF ADJUVANT OIL CAUSES ARTHRITIS IN DA RATS

The arthritogenic properties of adjuvant oil upon percutaneous adminis tration in DA rats was investigated. Groups of rats were administered single or repeated percutaneous applications of Freund's incomplete ad juvant (FIA) or olive oil on shaved skin with or without prior abrasio n of the skin. Control rats were shaved and abrased only. A transient arthritis developed in 8/16 animals after repeated applications of FIA on abrased skin. The incidence of arthritis increased to 7/8 animals when FIA was repeatedly administered via filter paper on abrased skin and covered with a bandage. Histological examination of the arthritic joints showed proliferation of the synovial lining layer, infiltration of mononuclear cells and polymorphonuclear cells in the subsynovial t issue. Some bone and cartilage destruction was also seen. Repeated tre atment with olive oil on abrased skin induced joint swelling in 3/15 a nimals, which did not, however, correspond to any microscopically obse rvable signs of inflammation. Also, a single application of FIA on abr ased skin or repeated applications of FIA without abrasion induced art hritis, although with low penetration, whereas control animals had no clinical signs of joint involvement. These findings demonstrate that p ercutaneous administration of adjuvant oil can cause arthritis in gene tically susceptible animals.