134 VITAMINS A AND CAROTENES 



laboratory by dirt'ct application oi \itainiii A solulions to the skin of mice, 

 and fully tlcscrihcd and illustrated for the rat, in a recent paper. ^'^ Xo effect 

 upon the skin of animals can be attributed to the internal absorption of 

 vitamin A other than those common to severe initritional disturbances in 

 general. 



Of the internal organs, the ath'enals exhibit changes, moderate in the rat, 

 conspicuous in the guinea pig. In both species the adrenal cortex enlarges. 

 There is loss of cortical lipids. The number of mitoses in the facsicular 

 zone greatly increases. In the guinea pig the glomerular zone atrophies and 

 mitosis in the fascicular zone often remains incomplete, with dispersion 

 and fragmentation of the chromosomes. Identical changes in the adrenals, 

 however, are a feature of experimental scurvy in the guinea pig and of 

 underfeeding in rats and guinea pigs.-^-^ It is possible, however, that 

 studies of the cortical lipids may reveal differences. Administration of 250 

 mg. of vitamin C given daily with the excessive amounts of \'itamin A do 

 not affect these adrenal gland changes in the guinea pig. 



The other endocrine glands of special interest, because of clinical reports, 

 are thyroid and hypophysis. A careful review of these glands from many 

 rats and guinea pigs, all of which had pronounced skeletal effects, re^'ealed 

 no constant histological change when compared with normal controls. The 

 anterior pituitary gland remained consistently normal in appearance in 

 sections stained by the eosin-methylene blue technique. The thyroid glands 

 varied in colloid content, vacuolization, staining, and height of alveolar 

 epithelium to about the same degree found in normal controls. Xo evidence 

 of inhibition of colloid secretion could be found. Even when compared with 

 thyroids from vitamin A-deficient animals, no conclusions were possible 

 from the histology that vitamin A has direct influence upon the thyroid. 

 A similar study of parathyroid glands from the same animals was mu'ewaiii- 

 ing, and the conclusion was una\'oi(lal)le that this gland is not pi-imarily 

 influenced by vitamin A. 



The lungs, the gastrointestinal tract, the pancreas inclutling the islands 

 of Langerhans — ^and the genitourinary system of both sexes exhibited no 

 effect of the hypervitaminosis. 



The liver occasionally showed minute necroses and usually loss of fat 

 vacuolization. Swollen endothelial cells of the sinusoids are the rule and 

 have been shown to be the result of excess A'itamin A storage."''' 



The spleen in all species showed some degree of hemosiderosis ;md fre- 



«J. I). Salu'lla, H. .\. JJcni, and H. II. Ivaliii, I'mr. Sor. /'J.rpll. liiol. Mel. 76, 4!»fl 



(1951). 

 " II. I'oppcc, I'htisiol. h'd's. 24, 20.') (11)41 1. 



