446 



ADVENTURES IX RADIOISOTOPE RESEARCH 



ganic P and to compare its activity with the total activity of the 

 muscle cells, assuming that only inorganic P can penetrate into the cells 

 and is afterwards largely combined in the cells. 



RESULTS 



The distribution of ^^Na and of ^^P between equal weights of plasma 

 and gastrocnemius muscle is seen in Table 1. The s^Na was administered 

 as 0.6 per cent sodium chloride solution which contained a negligible 

 amount of active sodium phosphate. The solution was injected into the 

 lymph sack of the frog. While, in experiments taking no more than 

 two hours, the phosphate solution was administered at the start of the 

 experiment, in experiments of longer duration a steadily decreasing 

 volume of the labelled P solution was injected at intervals of two hours 

 all through the experiment. Due to the uptake of the labelled phosphorus 

 by bone and other tissue, the ^2? concentration of the plasma strongly 

 decreases during an experiment unless kept up in this way. In the case 

 of sodium which is not taken up by the cells to any appreciable extent, 

 the 24Na concentration of the plasma does not much decrease with time. 

 In Table 1 it is seen that, while the apparent sodium space makes 

 out 4 per cent only of the weight of the muscle after the lapse of 3 min, 

 after 20 minutes 14 per cent are found, which almost corresponds to 

 the actual sodium space. The fact that between 20 minutes and 4 days 

 the ratio of the ^^Na content of plasma and muscle of equal weight 

 hardly changes is showing clearly that no significant uptake of 24Na 

 by the muscle cells takes place in the course of 4 days. 



Tablk 1. — Distribution of ^^Na and 32p, Res- 

 pectively, BETWEEN Plasma and Gastrocnemitjs(i) 

 OF Equal Weight at 22° 



The subscripts m and p represent muscle and plasma, respectively 



<i) The extracellular volume in per cent of the muscle weight is obtained by 

 multiplying the above figures by 97 (see p. 445). 



