142 Claude A. Villee 



Term placenta also retains its ability to respond to oestro- 

 gens added in vitro (Villee and Hagerman, 1953). The effect 

 of oestradiol-17/? or oestrone has been shown to be a stimula- 

 tion of isocitric dehydrogenase, an enzyme which requires 

 diphosphopyridine nucleotide (DPN) as coenzyme (Villee, 

 1955; Villee and Gordon, 1955; Gordon and Villee, 1955). 



The Metabolic "Ageing" of the Placenta 



From the present experiments it may be concluded that 

 in all of the metabolic functions tested, the activity of the 

 placenta decreases as gestation proceeds. If we may equate 

 decreasing metabolic activity with ageing, then the placenta 

 undergoes ageing. The changes observed include : an increase 

 in the solid fraction of the tissue, a decrease in oxygen con- 

 sumption to about half the rate earlier, a marked decrease in 

 the glycogen content of the tissue, a loss of the ability of the 

 placenta to synthesize glycogen in vitro, a decrease in the rate 

 of glucose utilization, a loss of the ability to produce glucose, 

 and less marked decreases in the rates of pyruvate utilization 

 and lactate production. 



A calculation of the fraction of the respiratory C0 2 derived 

 from the labelled substrate, obtained by comparing the specific 

 activities of the centre well C0 2 and the substrate, showed 

 that there was no change in this. The percentage of C0 2 

 derived from the glucose of the medium was 3 • 7 ±0 • 6 in the 

 early (10 week) placentas and 4-0 ±0-76 at term. The 

 percentage of C0 2 derived from the pyruvate of the medium 

 was 20 -8 ±1*34 in the early placentas and 18 -1^1*03 at 

 term. Thus, although the absolute amounts of glucose and 

 pyruvate metabolized by term placentas were decreased, the 

 relative proportion of the C0 2 derived from each of these 

 substrates was unchanged. 



Eight experiments have been performed with placentas 

 from women with toxaemia. The ages of the placentas 

 ranged from 32 weeks to term. In all respects tested, the 

 utilization of glucose, oxygen, glycogen, and pyruvate the 



