Effect of in vivo corticosterone and acute food deprivation on rat resident peritoneal cell chemiluminescence after activation ex vivo

Short-term effects of exercise on plasma very low density lipoproteins (VLDL) and fatty acids

PURPOSE

In the fasted state the lipid fuels for muscle metabolism are free fatty acids (FFA) released either from intramuscular triglycerides (TG), plasma albumin, or TG in circulating very low density lipoproteins (VLDL). The purposes of this study were to determine the influence of acute exercise of moderate intensity on 1) plasma total concentration of TG and VLDL components, 2) the plasma concentration and distribution of individual albumin-bound long-chain FFA, and 3) lipid peroxidation as measured by thiobarbituric acid reactive substances (TBARS).

METHODS

Eight healthy male subjects each participated in one exercise (EX) and one rest (RE) experiment. In EX the subjects exercised for 90 min at 58+/-5% (mean +/- SD) of maximal O2 uptake on a cycle ergometer followed by 4.5 h bedrest. RE followed the same protocol, but without exercise.

RESULTS

In EX there was no immediate change in VLDL concentration during the exercise. After exercise there was a decrease in VLDL, VLDL-TG, -cholesterol, -protein and -phospholipids compared with those after RE. There was no change in percentage composition of VLDL as result of exercise. Total plasma FFA concentration increased appreciably during exercise and remained elevated for several hours postexercise. There was no correlation between the change in FFA concentration and VLDL-TG. There was a significant positive correlation between the exercise-related increments in the various long-chain FFA, but the effect varied so that the relative abundance of oleic acid increased and that of stearic and arachidonic acid decreased during exercise. Plasma TBARS concentration increased during the day in both experiments.

CONCLUSION

The results indicate that there is a delay in the effect of an exercise bout on plasma VLDL and confirm that exercise affects various FFA in plasma differentially.

Granulocyte chemiluminescence response to serum opsonized zymosan particles ex vivo during long-term strenuous exercise, energy and sleep deprivation in humans

The chemiluminescence response of granulocytes to serum opsonized zymosan particles (SOZ) ex vivo was investigated during two ranger training courses lasting 7 days with continuous moderate physical activities corresponding to about 32% of maximal oxygen uptake or 35000 kJ.24 h-1, with energy deficiency (energy supply 0-4000 kJ.24 h-1), and less than 3-h sleep during the 7 days. Significant granulocytosis in combination with a lymphopenia in peripheral blood was observed during the whole course. A priming of the granulocytes for accentuated chemiluminescence response to SOZ was observed during the first days of the course with a maximal increase on day 3 in course A (+35% of control response) and on day 1 in course B (+12%). Thereafter, reduced responses to SOZ compared to control values (-28% and -21% in course A and B) were observed. In course A, a group (n = 8) receiving 5000 kJ.24 h-1 of additional energy, showed a more pronounced priming (maximum +57% versus +21% of control response) during the first days. In course B, all the cadets had 3 h of organised rest/sleep on day 5, and a second priming of the chemiluminescence response was observed on the subsequent 2 days. These data indicated that moderate, continuous, predominantly aerobic physical activities for 1-3 days around the clock primed the production of reactive oxygen species in granulocytes. This priming may be beneficial for, for example, host defence against micro-organisms, but may also contribute to inflammatory damage to normal tissues such as muscle, tendons and joints during exercise. However, when the moderate exercise continued for several more days, a down-modulation of the granulocyte response was observed. The findings of this study further support the possibility that moderate physical activity stimulates immunity, while more extreme duration of the same activities may result in a down-modulation of non-specific (and specific) immunity.

Dexamethasone and methylprednisolone affect rat peritoneal phagocyte chemiluminescence after administration in vivo

Production of reactive oxygen compounds by peritoneal monocytes/macrophages was studied in rats exposed to dexamethasone or methylprednisolone in the drinking water. Luminol-amplified chemiluminescence was measured in preparations of peritoneal leukocytes activated ex vivo by serum opsonized zymosan, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) or phorbol 12-myristate 13-acetate (PMA). After dexamethasone administration for 1 day (approximately 0.13 mg/kg per 24 h) a significant reduction in chemiluminescence was found in cells stimulated with serum opsonized zymosan, while responses to fMLP and PMA stimulation were significantly reduced after 2 days. The maximal inhibition obtained after 5-8 days of dexamethasone administration (plasma levels < 5 nM) was 92.0 +/- 1.2%, 87.6 +/- 0.2% and 84.5 +/- 3.1% in cells stimulated with serum opsonized zymosan, fMLP and PMA, respectively. Administration of dexamethasone or methylprednisolone for 48 h gave a dose-dependent reduction of chemiluminescence. ED50 values of dexamethasone were estimated at 0.06-0.15 mg/kg for the different stimulators (plasma concentrations 5-10 nM). Estimated ED50 values for methylprednisolone were 35-36 mg/kg. Since the percentage of mononuclear phagocytes in the peritoneal cell population did not change significantly with dose or time of dexamethasone exposure, this study indicates that glucocorticoids have a depressive effect on the monocyte/macrophage 'respiratory burst' in vivo. The results are consistent with the hypothesis that these effects are mediated by glucocorticoid receptors. Although the pathway activated by serum opsonized zymosan was more rapidly inhibited than the fMLP- and PMA-activated pathways, the responses induced by the different stimulators were similarly affected, suggesting a modulation of common components in the activation pathways, possibly protein kinase C or the NADPH-oxidase complex, after administration of low pharmacological doses of glucocorticoids in vivo.