Histology And Histochemical Study Of The Effect Of Hypervitaminosis A On The Choroid Plexus:

Esam Mohamed Gewaily

Fourty adult albino rats were utlized in this sutudy.Some were injected with vitamin A either In a singleextremely large dose to study the effect of acutehypervitaminosis A or in multiple large doses for 1,2 and 3months to show the effect of chronic hypervitaminosis A.Some of these injected animals were left for a period tostudy the effect of stoppage of vitamin A injection. Somerats were injected with arachus oil The rest of animalsserved as control. The choroid plexuses of all animals werestudied histologically with haematoxylin and eosin andhistochemically for adenosine triphosphatase and carbonicanhydrase enzymes.In the histologic study, vascular dilatation andengorgement were observed in hypervitaminosis A whetheracute of chronic.Adenosine triphosphatase and carbonic anhydraseactivity increased after injection of vitamin A. Theincreased activity of both enzymas denotes increasedcellular activity of the epithelial covering of the choroidplexus.Increased cellular activity and vascular dilatation andengorgement suggested increased secretion of cerebrospinalfluid after vitamin A injection.44The return of the choroid plexus to the resting stateafter discontinuation of vitamin A admiristration confirmsits role in increasing production of C.S.F. and inincreasing intracranial pressure.The strong enzyme activity occuring with mild vasculardilatation and engorgement in rats affected by acutehypervitaminosis A suggested that the vascular dilatation isan active hyperaemia which occurs when the tissues becomemetabolicaly more active as during exercise.