Histological studies on differntiation and systematization of vitamin A-storing cells in vertebrates.

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In order to know the heterogeneity of stored vitamin A in the hepatic stellate cells, we examined pig liver by the use of gold chloride method. Vitamin A-lipid droplet morphometry was performed under oil immersion and the calculated volumes were plotted on computerized maps. The hepatic lobule was sub divided into 5-zone/5-region comparmentalization. Distribution of values exhibited a district zonal gradient, higher at peripheral zones 1 and 2, dcreased over intermediate zone 3 toward centrilobular zones 4 and 5. Within a single zone, variations were obvious, forming a regional gradient ; higher at periportal than mideptal regions. Along the periphery, inlet venules of portal veins were quantified, revealing an occurrence rate of 60% at periportal, and 5% at midesptal regions.Abundant vitamin A was found in the mesangial cells in the lamprey kidney. We discussed similarities of the this cell type with the hepatic stellate cell. From our both present and previous findings on the lamprey, we concluded that vitamin A is stored in various splanchnic organs but not in the somatic organs. In the mammalian species, vitamin A is stored only in the liver, however, after the administration of excess vitamin A the fibroblastic cells in the splanchnic organs incorporated and stored it in the cytopalsm. Vitamin A-storing cell system is a system of mesenchymal cell system existing only in the splanchnic organs of vertebrates and vitamin A-storing cells reveal heterogeneity not only among splanchnic organs but also within a single organ.