Table 2. Respiration rate at low O₂ (15 μM) and low NO concentrations.

Respiration rate at 15 μM O₂ expressed as a percentage of respiration at 40 μM O₂ (before L-arginine addition) in cells treated with low doses of tetracycline (2, 5 and 10 ng/ml). Measurements of O₂ concentration and O₂ flux in control and NO-producing cells (1×10⁷ cells/ml) were taken in parallel chambers of a high-resolution respirometer (Oroboros Oxygraph-2k) at 37°C as explained in the Experimental section. NO production was initiated by the addition of L-arginine (1 mM) at 30 μM O₂. Values are the means ± S.D. for three independent experiments.

Tetracycline (ng/ml)	L-Arginine (1 mM)	Respiration at 15 μM (% of respiration at 40 μM)
2	+	98.4±1.7
	–	99.8±1.2
5	+	96.6±3.0
	–	99.7±0.5
10	+	97.1±0.8
	–	98.2±1.4