The Distribution of Radioactive Iodine (1-131) in Experimental Coccidioidomycosis

Iodine and its compounds have been used on an empirical basis in the treatment of various infectious diseases for many years. Its therapeutic efficacy in the past has been recorded in such diseases as the gumma of syphilis (1), North American blastomycosis, chromoblastomycosis and cryptococcosis (2). lodides are still recommended as specific therapy in sporo trichosis and their administration causes rapid improvement (3). lodides have been noted to have an adverse effect on the course of tuberculosis (4) and in some cases of North American blastomycosis (2). Two theories have been advanced to explain these adverse effects. The first is that iodides "dissolve" the fibrous tissue capsule which acts as a barrier in preventing dissemination of the infectious organism (4). The second theory is that the destruction of large numbers of organisms as the result of administration of iodides releases breakdown products which have a toxic effect on the patient (5). Although the exact site and modality of action of iodine is still speculative, the majority of investigators are of the opinion that iodine has little direct effect on the organism but modifies the host's response to the parasite. Skinner et al (6) cite evidence that Sporotrichuni schenckii survives in media containing a 10 per cent concentration of potassium iodide. They state that the therapeutic effect of iodides is due to their ability to stimulate the formation of fibrous tissue which tends to wall off the organisms. Jobling and Petersen (7) in a comprehensive study reviewed the early literature regarding the modality of action and proposed a theory which has received wide acceptance. They postulated that normally there are present in the blood and tissue enzymes or ferments which play an important part in the autolysis of necrotic tissues, tubercies and gummas. They found that these enzymes were rendered inactive by certain fatty acids present in the blood and in tubereulous caseous matter. They postulated that the therapeutic value of iodine was due to its ability to combine with the unsaturated fatty acids of the body and as a result lower the antitryptic (antienzyme) strength of the serum and of the tissues in general and permit the removal of dead matter by autolysis. Burke (8) in discussing the role of iodine in the treatment of syphilis felt that the predominantly lipoidal chemical character of the spirochete caused the production of excessive deposits of fibrous tissues and that this lipoid material also interfered with certain autolytic ferments of the blood which have the property of inhibiting the formation of such excessive fibrous tissue. He further stated that this neutralization was, in the main, due to the unsaturated lipoid radicals in the lipoid-rich material of the spirochete and that the therapeutic value of iodine was due to its ability to combine with these unsaturated lipoid radicals. Once the spirochetal lipoids are saturated they are no longer able to combine with enzymatic regulators of fibrin production and thus excessive fibrous tissue formation is prevented and the absorption of granulation tissue takes place. Irwin (9) discussed this point and sug-