Das Verhalten der energiereichen Phosphate in Froschmuskeln bei Steigerung der Kontraktionsamplitude infolge Substitution der Chlor-Ionen der Ringerl�sung durch andere Anionen (Br?, No 3 ? , J?, SCN?)

Abstract

If a frog's sartorius muscle is soaked in a modified Ringer's solution, containing bromide, nitrate or iodide in place of chloride the tension and duration of a twitch (Kahn and Sandow) and its heat production (Hill and Macpherson) are largely increased in the order Br<NO3<I. Thiocyanate proved to be even more potent than iodide. In a tetanic contraction, however, the tension, the heat production and the velocity of shortening are unaffected. In the present study the effects of the anion-modified media on the splitting of ATP and creatine phosphate have been investigated by means of paperchromatography. Obviously, the relative effectiveness of the foreign anions in increasing the twitch amplitude and the heat production is closely correlated to their ability to enhance high-energy phosphate breakdown. Therefore, during a single twitch, the anions exert their effects on the splitting of high-energy phosphates exactly in the same order, i. e. r Cl<B<NO3<I<SCN and, quantitatively, to a similar extent as they act on tension and heat production. In a maximal tetanic contraction, on the other hand, there is no specific influence of the anion-modified media on phosphate metabolism. Practically the same is true for the high-energy phosphates in resting muscles. It is concluded that the foreign anions enhance the splitting of ATP probably by increasing the Ca++-influx during excitation, thus leading to a potentiation of the biochemical and mechanical responses.