Influence of vitamin A palmitate on the growth of regenerating Triturus alpestris forelimbs.

The objective of this investigation was to analyse the effects of vitamin A palmitate orally administered to young postmetamorphic Triturus alpestris on the growth of regenerates. Vitamin A was administered for 4, 7, 11 and 14 days after amputation at the middle of the right zeugopod. Growth of regenerates was evaluated on the basis of external size measurements and blastema cell proliferation. Calculation of the percentages of cells in each cell-cycle phase and estimation of mitotic indices during the period of drug administration were performed by microdensitometric scanning of Feulgen-stained nuclei and counting of chromosome configurations, respectively. Vitamin A was found to induce polyploidism, to enhance transition from G1- to S-phase cell nuceli, to prolong the duration of G2-phase to the detriment of S-phase and to promote mitotic activity in the mesenchyme cells. In accordance with the above, an acceleration in the growth rates of treated blastemas with respect to controls was observed.