724 6. O-IODOSOBENZOATE 



rate always increases up to the final failure, whereas Jahn observed only 

 slowing. No conduction disturbances were noted. Since partial reversal can 

 be achieved by lengthy perfusion with o-iodosobenzoate-free medium, in 

 tissues some reduction of disulfide groups may occur. The dog heart-lung 

 preparation is quite resistant to o-iodosobenzoate, 100 mg producing no ef- 

 fect, although high doses increase the venous pressure, presumably by ini- 

 tiating cardiac failure (Mendez and Pisanty, 1949). 



The effects of o-iodosobenzoate on smooth muscles are at least superficially 

 similar to those on skeletal and heart muscle (Alanis, 1948). Isolated rabbit 

 intestine and the uterus in several species are put into a form of contrac- 

 ture, although this is eventually followed by relaxation and loss of aU rhyth- 

 mic activity. These actions are similar to those of iodoacetamide and ar- 

 senicals. 



Although the effects of o-iodosobenzoate in the whole animal indicate 

 marked effects on the central nervous system, no analysis of this has been 

 made so that sites and mechanisms are completely unknown. Frog nerve 

 axons are unaffected by 1 mM o-iodosobenzoate as measured by excitability 

 and conduction (Jahn, 1914). but the central actions are undoubtedly on 

 synaptic mechanisms. Neuroblastic damage has been found in developing 

 mice and rats after injections of o-iodosobenzoate, as with other SH re- 

 agents, but this probably relates more to growth and differentiation than 

 function (Hicks, 1953). 



EFFECTS IN WHOLE ANIMALS 



The earliest study of o-iodosobenzoate by Heinz (1899) is not ve»y illu- 

 minating since he administered potassium iodide simultaneously to generate 

 "nascent" iodine. However, he showed it to be irritant to the eye, the gas- 

 tric mucosa, and the peritoneum, and that this action seems to be due to 

 something other than its acidic properties. Loevenhart and Grove (1911) 

 confirmed the inflammatory action in the eye and subcutaneously, and show- 

 ed that intraperitoneal injections can be fatal as a result of the congestion 

 produced. Whether this is related in any way to the vesicant activity of 

 many SH reagents is not known. On the other hand, Bernheim et al. (1932) 

 found that injection into rabbits of o-iodosobenzoate inhibits conjunctival 

 edema induced by mustard oil. However, this could well be a nonspecific 

 action, since o-iodobenzoate and benzoate are somewhat active (as the am- 

 monium salts), and might well be mediated through the adrenal cortex. 



Loevenhart and Grove (1909, 1911) investigated the pharmacological 

 properties of o-iodosobenzoate and related compounds because they believed 

 that the oxygen of this substance is physiologically active and can be used 

 by the tissues; e.g., o-iodosobenzoate alone does not oxidize phenolphthalin 

 to phenolphthalein, but does if some serum is present, this being interpreted 



