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.