EFFECT OF IN-VIVO CORTICOSTERONE AND ACUTE FOOD-DEPRIVATION ON RAT RESIDENT PERITONEAL CELL CHEMILUMINESCENCE AFTER ACTIVATION EX-VIVO

Adrenoglucocorticoid regulation of rat peritoneal monocyte/macrophage function was studied by exposing rats to corticosterone (CS) in the dr inking water, and to fast (48 h). Production of reactive oxygen metabo lites was measured by luminol amplified chemiluminescence (CL) in prep arations of peritoneal cells activated by serum treated zymosan (STZ). Administration of CS which led to an increase in plasma CS from 31 (c ontrols) to 46 ng mL(-1), reduced CL (per cell) by 31%. Fast, which di d not change plasma CS or ACTH, also had an inhibitory effect on CL (- 25%), while the combination of CS administration and fast strongly inh ibited the CL (-89%), indicating that plasma CS and fast reduced CL in a synergistic way. Similar effects on cell number were observed: CS-a dministration, fast and the combination reduced macrophage numbers (-1 3, -19.7 and -55%), while no significant effect was observed on the nu mber of monocytes. The effect of adrenalectomy (adx) was studied in an other series of experiments; adx induced no significant change in peri toneal leucocyte number or composition, while cells from adx animals h ad significantly higher chemiluminescence reaction than cells from sha m operated animals. CS substitution in adx animals reduced CL by 30% w hile sham operated animals had 49% lower CL in adx. The data from adx animals also suggest that endogenous levels of CS are inhibitory for C L, but the results are not conclusive for the effect of very low doses of CS since other mechanisms than elimination of CS could prime the c hemiluminescence reaction after adx. In conclusion, a moderate elevati on of CS after systemic administration ill vivo reduced the total numb er of mononuclear phagocytes in rat peritoneum, reduced the relative n umber of macrophages compared with monocytes, and suppressed the funct ion of monocytes/macrophages by reducing the production of reactive ox ygen molecules in activated cells. Furthermore, the effect of corticos terone was also dependent on the physiological situation, since the ef fects of fast and corticosterone were synergistic.