Effect of Vitamin A on Pulmonary Macrophage Mobilization in Hamsters Exposed to Cigarette Smoke.

Abstract

Male Syrian golden hamsters fed either vitamin A-free diet or normal stock diet with or without vitamin A supplementation were subjected to cigarette smoke inhalation for 6 weeks to study the relationship between the pulmonary cell response and vitamin A intake. All surviving animals after the last smoke exposure were killed for analysis of plasma and liver vitamin A contents and histopathology of the lung. Plasma and liver vitamin A levels were apparently lower in hamsters fed vitamin A-free diet than those maintained on normal stock diet. Liver vitamin A content was significantly higher in vitamin A-supplemented hamsters than those on stock diet alone, although there was no significant difference in plasma vitamin A level. Histopathologically, the number of free macrophages was counted in lung sections stained with hematoxylin and eosin and the count was used as the index to evaluate smoke-related insult at different levels of vitamin A. The number of macrophages was significantly greater in the smoke-exposed hamsters on vitamin A-free diet than those on normal stock diet. However, there was no significant difference in the macrophage count between vitamin A-supplemented and unsupplemented hamsters on stock diet. These results indicate that vitamin A deficiency and smoke exposure appear to enhance pulmonary macrophage mobilization. It is possible that the respiratory epithelium of vitamin A-deficient hamsters loses its integrity and becomes susceptible to injury by irritants such as those present in cigarette smoke. The elevated pulmonary free macrophage count may be a response to the damage caused by vitamin A deficiency and smoke exposure.