TISSUE FUNCTIONS 709 



in cardiac muscle also (page 710), and is not the result of membrane depolar- 

 ization. However, soaking frog muscle in 10 mM arsenite abolishes the 

 resting potential after 4 hr, and it was postulated that pyruvate oxidation 

 and the operation of the cycle are involved in the maintenance of the po- 

 tential (Ling and Gerard, 1949). Arsenite at concentrations as high as 

 100 mM does not alter muscle after- potentials (Macfarlane and Meares, 

 1958). Relatively little work has been done on glycerinated muscles and 

 preparations of the contractile proteins, but it has been observed that oxo- 

 phenarsine at 0.1 mM reversibly abolishes the ATP-induced contraction 

 of nonconducting rabbit psoas muscle (Korey, 1950), at 0.5 mM inhibits 

 the contraction of actomyosin and the polymerization of actin (Turba 

 and Kuschinsky, 1952), at 0.8 mM inhibits the ATPase activity and the 

 superprecipitation of actomyosin (Mugikura et al., 1956), and at 0.7 mM 

 inhibits myosin ATPase and the formation of actomyosin in parallel fashion 

 (Barany and Barany, 1959 a). The viscosity and Ca++-binding of actin 

 are not much altefed by 2 mM oxophenarsine, in contrast to the potent 

 effects exerted by the mercurials (Barany et al., 1962). It is difiicult to 

 extend these results to intact muscle but clearly the arsenicals can directly 

 affect certain contractile processes. 



Smooth Muscle 



Despite the well-known effects of arsenicals on the capillaries and the 

 gastrointestinal tract, no detailed studies of the actions on these smooth 

 muscles, or others, have come to my attention. The intestinal edema, the 

 serous and mucosal hemorrhages, and the gastric and intestinal erosions 

 seen in arsenic poisoning (Cameron et al, 1946) have been generally assumed 

 to be caused by vascular damage rather than a major direct effect on the 

 gastrointestinal tract. The contractile amplitude of isolated rabbit intestine 

 is depressed by 0.4 mM arsenite, while 4 mM abolishes contractions with 

 the intestine in a relaxed state (Joachimoglu, 1915). Alanis (1948) pointed 

 out that oxophenarsine produces the same effects on smooth muscle as on 

 skeletal muscle and the heart, and showed that the isolated rabbit intestine 

 and the uteri of various species respond by an initial contraction followed 

 by relaxation and loss of rhythmic activity. It may be recalled that, in the 

 early work of Lesser (1878 c) and Pistorius (1883) on the in vivo responses 

 of the intestine to arsenite, an initial increase in peristalsis or tetanic con- 

 tractions, or both, was observed, these effects not being much altered by 

 denervation. One might imagine the initial stimulation to be due to hista- 

 mine release, since the mercurials have been shown to do this, but arsenite 

 does not release histamine from the cat intestine (Bachmann, 1938) and, 

 in fact, inhibits the release of histamine by the releaser. Compound 48/80 

 (VanArsdel and Bray, 1961), and anaphylaxis (Chakravarty, 1962). The 



