Effects of 5-fluorouracil on collagen synthesis during quail secondary palate development

A study was undertaken to examine the involvement of collagen synthesis during palate development in quail where mammalian-type shelf reorientation is absent. Teratological observation showed that 100 micrograms 5-fluorouracil (FU) on day 4 of incubation increased the gap between the palatal shelves. Light microscopic observation indicated that the quail palatal shelves develop as horizontal ridges on day 5 and approximate on day 8 of incubation but never fuse. FU treatment affected the approximation of palatal shelves. In separate experiments, both the control and FU-treated quail embryonic palates, which were dissected between days 5 and 10 of incubation, were incubated in a growth medium supplemented with 14C-proline. The rate of collagen synthesis, total protein, hydroxyproline (HYP) levels, and collagen isotype were determined. The result showed that in control palates the rate of collagen synthesis increased fivefold between days 6 and 8 of incubation but dropped thereafter. In FU-exposed palates, the rate of collagen synthesis was lower than that in controls. It increased threefold between days 7 and 8 of incubation. High performance liquid chromatographic measurement of HYP levels indicated that, in comparison to controls, HYP accumulation in FU-treated palates was reduced by 50% on day 6 and 75% on day 8 of incubation. Total protein content in FU-treated palate were also 50-70% lower than those in their control counterparts between days 5 and 10 of incubation. Gel electrophoresis showed that only type I collagen was synthesized in the developing palate of both the control and FU-treated quail embryo. An analysis of results of the present study, along with the data from literature on mammals, corroborate the proposition that an increased collagen synthesis may contribute to the acquisition of volume of vertebrate's secondary palatal shelf for its continuing morphogenesis.