Effect of various stressors on muscular contraction induced by NaH2PO4 and NaClO4

Abstract

Experiments in the rat indicate that the motor disturbances elicited by sudden overdosage with NaH2PO4 and NaClO4 are qualitatively different. NaH2PO4 produces a tetany-like condition, with generalized continuous tremor and occasional fits of generalized clonic convulsions. NaClO4, on the other hand, induces no tremor, but rather persistent, tonic extensor cramps, predominantly in the hind legs. Among a great variety of stressors, only those associated with increased muscular work (exercise in a revolving drum, forced restraint, electric shocks) enhanced the susceptibility to acute NaH2PO4 intoxication, while all the stressors that were examined elicited marked muscular contractions following treatment with threshold doses of NaClO4. These effects of NaH2PO4 and NaClO4 are not due to the Na-ion as such, since equimolecular amounts of NaCl were totally ineffective in producing muscular contractions. It appears that an excess of NaH2PO4 and NaClO4 interferes rather selectively with the biochemical processes responsible for muscular contraction; hence, these salts induce fatigue and muscle dysfunction, following comparatively brief periods of exercise. In addition, the muscular action of NaClO4 (unlike that of NaH2PO4) is greatly enhanced even by stressors which do not act preponderantly upon muscle.