Discussion 145 



differences between normal and toxaemic placentas either. He had 

 3 or 4 toxaemic placentas, and as you know they are not too easy to 

 come by. It is only because our laboratory is in a lying-in hospital that 

 we have been able to get as many as we have. 



Amoroso : What part of the placenta, Professor Huggett, would you 

 say was implicated in maternal glucose production ? 



Huggett: I have no knowledge at all about the site of production of 

 glucose in any species. 



Williams: Do I detect in this discussion of glucose production and 

 chemical function a suggestion that these are intrinsically regulated 

 within the placenta, or are they determined by the hormone conditions 

 in the maternal organism ? If glucose production decreases, does that 

 mean anything except that there is no longer any need for the extra 

 amount of glucose that there was earlier and that the greater need of 

 the foetus earlier called in some change in the maternal organism to 

 stimulate an extra production of glucose ? 



Villee: I do not know if we can speak in terms of need. I think 

 Prof. Wislocki mentioned the histochemical evidence that the foetal 

 liver is unable to store glycogen and secrete glucose early in pregnancy. 



Williams: It was only a suggestion that there was a need. 



Villee: Simply, in order to have a developing foetus, we must have 

 some organ capable of regulating the glucose content of the foetal 

 blood. The foetal liver cannot do it but the placenta very fortunately 

 can. When the foetal liver takes over this function there is no longer 

 any need for the placental enzyme and its function declines. I do not 

 really know what is cause and what is effect, but this observation is 

 quite general in enzyme phenomena. It is known that so-called adaptive 

 enzymes occur widely in bacteria and examples of comparable enzyme 

 changes are being found more and more in animal tissue and mammalian 

 tissue. These are changes in enzyme activity and, presumably, in the 

 actual amount of enzyme present, in response to the hour by hour needs 

 for that particular enzymatic activity. The observation that when there 

 is no longer any need for the secretion of glucose by the placenta, the 

 enzyme glucose-6-phosphatase declines and disappears, suggests that 

 this is an example of enzyme adaptation. 



Williams: Do you think you could recover that activity? 



Villee: I really do not know. 



Williams: What happens, for instance, in a diabetic pregnancy? 



Villee: We have tested quite a few diabetic placentas and they were 

 no different from the normal ones. 



Williams: But, of course, they are controlled anyway by the insulin 

 given to the mother throughout pregnancy. 



Villee: Yes, but we have had some diabetics which were in rather poor 

 control and even their placentas showed no differences. 



Yemm: May I ask Dr. Villee whether during the course of his experi- 

 ments with radioactively labelled glucose, he measured the rate of 

 incorporation into glycogen ? Does the glycogen decline result from 

 higher rate of breakdown or slower rate of synthesis ? 



Villee: Early in gestation there is a very active incorporation of 



