Fig. 1From: Vitamin A depletion induced by cigarette smoke is associated with an increase in lung cancer-related markers in ratsRetinoic Acid Level in Lungs Exposed to Cigarette Smoke. The all-trans retinoic acid level in lungs exposed to different doses of cigarette smoke for 6 weeks. Values are mean ± SEM, n = 6. Groups with different letters are significantly different, P < 0.05Back to article page