Fig 4.

Tulathromycin induces apoptosis, but not necrosis, in bovine macrophages in vitro in a time- and concentration-dependent manner. Apoptotic mono-and oligonucleosomes (A) and secreted lactate dehydrogenase (LDH) (B) were measured in bovine macrophages incubated with IMDM alone (control [ctrl]) or treated with tulathromycin (0.1 mg/ml or 1.0 mg/ml) for 2 h, 6 h, 12 h, or 20 h at 37°C. A separate set of experiments then measured mono-/oligonucleosomes (C) and LDH release (D) in bovine macrophages incubated under similar conditions, but for a longer period of 48 h. Values were calculated as absorbance ratios versus values measured in control macrophages arbitrarily set to 1.0. Staurosporine (stauro; 1 μM) served as a positive apoptotic control. Cells exposed to 2% Triton-X (TX-100) served as a total LDH control. Values are means ± SEM. n = 6/group. *, P < 0.05; **, P < 0.01; ***, P < 0.001 versus control at each time point.