HCS regulation in cultured placenta: action of glucose

The regulation of HCS secretion on placenta cultures in the presence of [3H] leucine was studied. When Eagle's medium containing 0.0055 M of glucose per liter is used, it is noted that the HCS increases regularly in the culture medium, whereas it diminishes in the explants. [3H] HCS represents about 50% of the [3H] proteins, and among these proteins HCS is preferentially secreted in the culture medium. The absence of glucose in the medium provokes a decrease in all of the cellular metabolism as well as a decrease in protein and HCS secretions, with an accumulation of preformed HCS in the tissues. An increase in the glucose level in the medium 0.011 and 0.027 M provokes a selective decrease of HCS secretion with an accumulation of preformed HCS in the tissues, determing a long term decrease in HCS synthesis. Insulin added in the mediums (60 microU/ml) does not change the results significantly. The use of structural analogues of the glucose shows that the point of impact of the HCS secretion regulation by the glucose is membranous; however, it seems that at a second stage one or some glucose metabolites also interven. There is no self regulation of HCS secretion in vitro.