The objective of this study was to examine the effect of increased ambient temperature on Hsp70 expression, superoxide dismutase (SOD) activity, nitric oxide (NO), malondialdehyde (MDA), caspase 8, caspase 9 and caspase 3 in relation to the intrinsic and extrinsic apoptosis pathway (IAP and EAP) of broiler blood cells (BBC). BBC were maintained at 42 °C and at 5 ranges of temperatures; 42-43, 44-45, 46-47, 48-49, and 50-51 °C. Then Hsp70 expression, SOD activity, NO, MDA, activity of caspase 8, caspase 9 and caspase 3, and living and apoptotic BBC were measured. It was found that Hsp70 expression and SOD were increased at 42-43 °C (P < 0.05), while the activity of caspase 9 and caspase 3 decreased (P < 0.05). At higher temperatures of 44-45 °C, caspase 9 and caspase 3 activities were increased and were higher than at 42 °C (P < 0.05). Apoptosis commenced in the temperature range 46-47 °C; during this range of temperature, NO increased (P < 0.05), but it decreased at 48-49 °C (P < 0.05). At the same time, activity of SOD in BBC was increased, achieving the highest levels (P < 0.05). In addition, activity of caspase 8 and caspase 3 at 48-49 °C was higher than that at 42 °C, and the apoptotic BBC was increased (P < 0.05). Therefore, temperature effects on BBC could be divided into three phases. The first phase was the temperature at 42 °C. The second phase, or pre-apoptotic phase, was in the temperature range from 42 to 45 °C. The third phase was the apoptosis phase, which manifested at 46 °C and above. These phenomena showed that in the pre-apoptosis phase, Hsp70 suppressed the IAP. On the other hand, in the apoptosis phase, apoptotic BBC is caused by the influence of NO, superoxide and MDA through the EAP.
Keywords: Apoptosis; Broiler blood cell; Caspase activity; Heat stress; Nitric oxide; Oxidative stress.
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