INVIVO AND INVITRO STUDIES ON THE EFFECTS OF VITAMIN-A ON THE CHEMILUMINESCENT RESPONSE OF MURINE PERITONEAL-EXUDATE CELLS

Retinoids are known to enhance macrophage function and enhance bacterial clearance during experimental infection. The purpose of these experiments was to determine if one indicator of macrophage activation, chemiluminescence (CL), was enhanced by retinoids. Peritoneal exudate cells (PEC) harvested from mice injected intraperitoneally for 5 days with retinol palmitate (25, 125, or 250 U/g body wt./d) showed significantly enhanced chemiluminescence (CL) when exposed to opsonized zymosan. A direct dose-response effect was observed, in that the more retinol palmitate was injected, the more CL was observed. The same dose of retinol palmitate injected subcutaneously did not result in enhanced CL. In vitro incubation of murine PEC with physiological concentrations of retinol palmitate or retinoic acid for 1, 6 or 24 h did not result in enhanced CL. The reasons for the effect of the route of administration of retinol palmitate are unknown, but may include poor absorption from the site of subcutaneous injection or an adjuvant effect when injected intraperitoneally due to the particulate nature of the water-dispersible retinol palmitate preparation.