The content of water, protein, DNA, RNA and sugar in fetal rat palatal processes during reorientation and fusion

Growth of developing palatal processes was studied from the time the processes first appeared to their reorientation and fusion to form the secondary palate. Wet weight, dry weight and macromolecular content of the processes were quantified at half-day intervals. There was a steady decrease in the relative water content of the processes, despite a tenfold increase in total mass. Total protein, DNA and RNA increased steadily and maintained their relative abundance. The accumulation of hexose sugars, however, was erratic, a sharp rise in relative sugar content corresponded to the period of process reorientation before fusion. The results suggest that growth of the palatal processes is continuous and that a period of rapid growth cannot account for process reorientation; they do not support the hypothesis that increased turgor due to hydration of polysaccharides provides the active force for process reorientation.