EVIDENCE THAT HALOTHANE ANESTHESIA INDUCES INTRACELLULAR TRANSLOCATION OF SURFACE-COAT AND GOLGI RESPONSE IN EQUINE PULMONARY INTRAVASCULARMACROPHAGES

The pulmonary intravascular macrophages (PIMs) of horse contain a uniq ue electron-dense globular surface-coat which is arranged in a linear fashion in conformity with the contours of the cell membrane. The coat is sensitive to heparin treatment and to the digestive effect of lipo lytic lipase, suggesting that the coat is predominantly composed of li poproteins. During the present study, ultrastructural features of PIMs were analysed after exposing horses to halothane inhalation which was chosen as the model agent of lipid-soluble anaesthetic. The surface-c oat showed acute sensitivity to halothane by disappearing almost compl etely from the surface after 1-2 h of exposure. The cell membranes wer e thrown into extraordinary arrays of lamellipods, pseudopods and veil s. Concurrently, the globular units of the coat were translocated into the endosomal-lysosomal system, most probably via receptor-mediated e ndocytosis. There was a high profile of the expanded Golgi apparatus e specially the trans Golgi network (TGN) in close association with the centrioles and microtubules. Cytochemistry revealed an enrichment of t he Golgi complex with acid phosphatase activity. On the other hand, ha lothane showed an inhibitory effect on the lysosomal acid phosphatase of the PIMs. It is proposed that the Golgi response occurred as an obl igatory concomitant of internalization of the surface-coat and its sub sequent passage through endosomal-lysosomal system. The acid phosphata se activity as a marker enzyme of the expanded Golgi is correlated wit h metabolic effects of the internalized coat which is unique to the pu lmonary intravascular macrophages. Furthermore, the intense expression of acid phosphatase at the Golgi level of the PIMs may signify a comp onent of secretory phenotype in order to produce vasoactive mediators at the onset of stressful stimuli triggered by the halothane anesthesi a.