UPTAKE OF RADIO-POTASSIUM ( 42 K) BY THE 

 UTERUS AND PLACENTA DURING THE AD- 

 VANCEMENT OF PREGNANCY IN THE RAT 

 AND THE GOAT 



R. J. Harrison and J. L. D'Silva 



Anatomy and Physiology Departments, London Hospital Medical College, 



London, E.l 



During recent years increasing use has been made of 

 experiments involving the introduction of radioactive sub- 

 stances into the maternal circulation in order to examine 

 placental uptake of various substances. Such experiments 

 have been carried out in several species at varying stages of 

 gestation, using radioactive sodium (Flexner and Roberts, 

 1939; Flexner and Pohl, 1941; Flexner and Gellhorn, 1942), 

 iron (Vosburgh and Flexner, 1950), phosphorus (Nielson, 1941 ; 

 Naeslund, 1951), calcium (Shirley, Jeter, Feast er, McCall, 

 Outler and Davis, 1954) and strontium (Finkel, 1947) as 

 tracer substances (for further references see also Reynolds, 

 1949 and Marshall, 1952). 



The distribution of injected radioactive potassium ions 

 (as] 42 KCl) in animal tissues has been investigated by a number 

 of workers (see D'Silva and Neil, 1951, for earlier references; 

 Walker and Wilde, 1952; and Ginsburg, 1952). Their results 

 show that the cells of organs such as the liver and kidney 

 rapidly exchange their potassium with that of the plasma, 

 whereas skeletal muscle cells and red cells exchange their 

 potassium slowly. Since no experiments had been reported 

 on the distribution of radioactive potassium ions injected in 

 tracer amounts into pregnant animals the authors carried out 

 a series of experiments on pregnant and non-pregnant rats 

 (D'Silva and Harrison, 1953). The distribution of potassium 

 was studied at different times after injection and at various 



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