[Increase in heat production by muscle contraction caused by 2,4-dinitrophenol].

By means of a highly sensitive thermometric method (1.10--50 C/mm) it was possible to demonstrate that the heat production during a single contraction of the isolated rat diaphragm increased under the influence of 2,4-dinitrophenol (DNP). Low DNP concentrations failed to produce any manifest changes in the resting muscle, but its action was distinct during contraction. With the same muscle contraction force DNP action was followed by an increase (about 1 1/2-fold) of heat production. This fact confirmed a supposition on the leading role of oxidation and phosphorylation uncoupling in the muscle cell respiratory chain in the increase of muscle contraction heat production in the animals after cold adaptation.