In vivo effect of ascorbic acid on neutrophil function in healthy and dexamethasone-treated cattle

Ascorbic acid (20 mg/kg of body weight) administered subcutaneously to otherwise nontreated cattle resulted in enhancement of neutrophil oxidative metabolism and capability of neutrophils to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Random migration, bacterial ingestion, and iodination by neutrophils was unaffected. Three dosage levels of ascorbic acid (10 mg/kg, 20 mg/kg, and 40 mg/kg) were examined for their effects on neutrophil function in cattle treated with dexamethasone (0.04 mg/kg). Dexamethasone administration caused an enhancement of neutrophil random migration and a suppression of neutrophil oxidative metabolism, iodination, and ADCC. None of the dosage levels of ascorbic acid had an effect on the alterations in the WBC count induced by dexamethasone. The ascorbic acid did tend to reverse the effects of dexamethasone on neutrophil random migration, oxidative metabolism, and ADCC in a dose-dependent manner, with the lowest dose having no discernible effect. Ascorbic acid administration also tended to enhance Staphylococcus aureus ingestion by bovine neutrophils. These results indicate that ascorbic acid should be further investigated for its potential to reduce the susceptibility of stressed or glucocorticoid-treated cattle to infective processes.