Expression of hypoxia-inducible factor 1α mRNA in hearts and lungs of broiler chickens with ascites syndrome induced by excess salt in drinking water.

Hypoxia-inducible factor 1 (HIF-1) is a ubiquitously expressed heterodimeric transcription factor that mediates adaptive responses to hypoxia in all nucleated cells of metazoan organisms. Hypoxia-inducible factor 1α is involved in the pathogenesis of pulmonary hypertension in humans and animals, but whether HIF-1α is associated with the development of pulmonary hypertension syndrome (also known as ascites syndrome, AS) in broiler chickens has not been determined. In the present paper we addressed this issue by measuring the expression of HIF-1α mRNA in hearts and lungs of broiler chickens with AS induced by excess salt in drinking water. We conducted 2 experiments. The first experiment was used to observe the effects of excess salt on AS incidence. The results indicated that total incidence (20%) of AS in excess salt group (receiving 0.3% NaCl in drinking water) was much higher compared with the control group (receiving tap water) over a 43-d time course (P < 0.05). In the second experiment, we determined mean pulmonary arterial pressure (mPAP), ascites heart index (AHI), and expression of HIF-1α mRNA in lungs and hearts of broiler chickens after the excess salt treatment. Our results showed that excess salt induced pulmonary hypertension (indicated by higher mPAP) and right ventricular hypertrophy (greater ascites heart index) in broiler chickens. Meanwhile, the expression levels of HIF-1α mRNA in lungs and hearts were significantly increased at different time points in the excess salt group compared with the control group. Linear correlation analysis showed that the expression of HIF-1α mRNA in lungs was significantly positively correlated with mPAP (correlation coefficient = 0.79, P < 0.001), demonstrating that expression of HIF-1α mRNA was gradually increased in the excess salt group with the increase of pulmonary arterial pressure. In addition, the ascitic chickens showed significantly higher transcriptional levels of HIF-1α in hearts and lungs, compared with the age-matched healthy chickens, respectively. Our findings hinted that HIF-1α might be associated with the development of AS induced by excess salt in drinking water in broiler chickens.