G08 IX. CAROTENOTDS AND VITAMINS A 



eified, and is disposed of by osteoclasis. Studer"^^ states that hyperplasia 

 begins between the diaphysis and the epiphysis. 



Hypervitaminosis A also causes changes in the teeth. According to 

 Nieman and Klein Obbink,""^ the incisor teeth present pathologic changes, 

 but Pohto^^-^ confirmed this finding only in part. A reduction in the for- 

 mation of dentine occurs, together with thinning or disappearance of the 

 lingual alveolar bone.^^^^ RodahP^" is of the opinion that hypervitamino- 

 sis A causes a deposit of calcium in the pulp and dentine, and degeneration 

 of the odontoblasts. Fell and Mellanby^^^^"^'^" developed in vitro methods 

 for studying the effect of an excess of vitamin A on bone tissue. They 

 noted resorption and disappearance of the fetal bone tissue in vitro, and 



dwindlmg of the cartilage matrix, which sometimes disappeared com- 

 pletely. 'i^s-nso 



c. Hemorrhage and Inflammation of Mucous Membranes. Internal 

 hemorrhage is a characteristic reaction following hypervitaminosis A 

 in experimental animals, and especially in rats. Hemorrhage occurs chiefly 

 in the older animals, in contradistinction to bone fractures, which are 

 observed principally in the younger ones. The hemorrhages may be sub- 

 cutaneous and intramuscular, although they occur chiefly in the lungs and 

 viscera. Walker et aZ.^^^^ reported that excessive doses of vitamin A in- 

 crease the prothrombin time in the rat. Although this animal is able to 

 synthesize vitamin K in the intestinal tract, about 90% of the rats suffering 

 from hypervitaminosis A die as a consequence of hemorrhage, when they 

 are on a vitamin K-free diet."'- RodahP'^' confirmed the hypothesis 

 that hemorrhage is a s>Tnptom of hypervitaminosis A. 



d. Endocrine Symptoms. Definite changes in some of the endocrine 

 organs result from hypervitaminosis. The adrenal glands present the 

 most conspicuous change when an excess of vitamin A is present ; the effect 

 is mild in the rat and more noticeable in the guinea pig. The changes 

 which occur in the adrenals of the guinea pig in hypervitaminosis A are 



11^^ A. Studer, Verhandl. schweiz. naturforsch. Ges., 128 Jahresversamml. (St. Gallen), 

 1948, p. 182. 



1126 ]\j Pohto, Mikroskopische Untersuchungen iiber die Schneidezdhne der Ratten 

 bei der A-Avitaminose, der Heilung derselben, und der A-Hypervitaminose, Diss. Med. 

 Chem. Lab. Odont. Inst., Univ. Helsinki, 1938; cited by S. B. Wolbach and O. A. 

 Bessey, Physiol. Revs., 22, 233-289 (1942), p. 236. 



11" K. Rodahl, Nature, 164, 531 (1949). 



1128 H. B. Fell and E. Mellanby, Brit. Med. J., 1950, II, 535-539. 



1129 H. B. Fell and E. Mellanby, J. Physiol, 115, 4P-6P (1951). 



1130 H. B. FeU and E. Mellanby, /. Physiol, 116, 320-349 (1952). 



11" S. E. Walker, E. Evlenburg, and T. Moore, Biochem. J., 41, 575-580 (1947). 

 i"2 C. L. Maddock, S. B. Wolbach, and D. Jensen, Federation Proc, 7, 275 (1948). 

 11" K. Rodahl, Hypervitaminosis A, Norsk Polarinstitutt Skr., No. 95, 1-206 (1950). 



