Effects of intra-tracheal application of vitamin A on concentrations of retinol derivatives in plasma, lungs and selected tissues of rats.

Vitamin A deficiency results in typical morphological alterations of the respiratory mucosa (increase of goblet cells, decrease of ciliated cells, squamous metaplasia). This early effect of the deficiency is an explanation for the frequency, severity and persistence of the respiratory infectious diseases that have been responsible for high mortality in vitamin A-deficient children. Vitamin A supplementation leads to rapid reduction in morbidity and mortality. However, in many cases oral supplementation is not very effective due to gastrointestinal diseases with impaired absorption of the fat soluble vitamin. To overcome this problem we developed an inhalable vitamin A-ester and administered the vitamin through a tracheostoma in vitamin A-sufficient (n = 8) and vitamin A-deficient rats (n = 8). 15 minutes after inhalation the retinyl ester appeared in the blood and was detected (6 h after inhalation) in lung, testicle, liver, kidney and small intestine. The unphysiological retinyl ester (odd number of C-atoms) was rapidly hydrolysed and reesterified with physiological fatty acids (palmitate). The results of our study demonstrate that the inhalative application circumvents problems of oral administration and results in a sufficient supply to sensitive target tissues.