Ultrastructural effect of L-ascorbic acid 2-phosphate on cultured keratocytes.

I studied the effect of L-ascorbic acid 2-phosphate (P-Asc), a long-acting derivative of L-ascorbic acid, on the fine structures of cultured rabbit keratocytes. The results showed that cells cultured with 0.1 mM P-Asc for 30 days were more markedly multilayered than those grown without P-Asc. Dilation of the cisternae of the endoplasmic reticulum in the control cells indicated an accumulation of protein (probably procollagen). In addition, many lysosome-like structures, which may degrade underhydroxylated procollagen, were observed in the cytoplasm of the control cells. A slight increment of free ribosomes was also found within the control cells. P-Asc enhanced the multilayerization of cultured keratocytes. We conclude that the changes seen in the cytoplasm are due to the effect of P-Asc acting as vitamin C.