Effects of Heat Stress on Histological Features in Pituicytes and Hepatocytes, and Enzyme Activities of Liver and Blood Plasma in Japanese quail (Coturnix japonica)

Abstract

Two experiments were conducted to ascertain the histological features in pituicytes and hepatocytes and the enzyme activities of liver and blood plasma at 8 weeks of age in Japanese quail (Coturnix japonica) exposed to high environmental temperature. The birds were divided into two groups. The control group was kept under a constant temperature of 26°C, and the heat stress group was kept at 40°C, with the same 60% relative humidity, for 2 weeks. The birds under heat stress became weary, showed higher panting and water consumption, and had lower body weight gain and feed intake than the control birds. The body temperature of the birds in both conditions was in the same range from 40.8 to 41.4°C. The paraffin sections of the pituitary and liver, stained by HE and PAS, and the frozen sections, stained by Oil Red O, were used for ascertaining histological changes in the organs of two male and two female birds. Under heat stress, the testis, the ovary, and the liver of birds shrank. The pituicyte and hepatocyte changed in conformation, shape, size and amount of lipid droplets. The nucleus conformation shrank. The cytoplasm surrounding the nucleus showed a peripheral pallor and signs of necrosis, and the composition became acidic. The liver and pituitary showed a decrease in the size and amount of small and large of lipid droplets. Enzyme activities were obtained from four male and four female birds. The glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), and lactic dehydrogenase (LDH) enzymes in the blood plasma of the birds exposed to high temperature in both sexes increased significantly (P<0.01). However these enzymes decreased significantly (P<0.01) in the liver due to heat stress. This study showed that there were the histological features of the hepatocyte changes resulting from prolonged heat stress. It is reasonable to assume that the functional reserves of the liver which are needed to serve the physiologically demanding reproductive processes in the birds are sufficiently depleted under heat stress to cause a shortage of materials needed to fully support these processes. This study suggests that heat stress has an effect on the pituicytes and hepatocytes, bringing about necrosis, and that the GPT, GOT, and LDH decrease in the liver, but increase in blood plasma in Japanese quail.

Keywords

• heat stress
• pituicyte
• hepatocyte
• enzyme activities
• japanese quail