Apoptosis in the small intestine of neonatal rat using blue light-emitting diode devices and conventional halogen-quartz devices in phototherapy

Phototherapy is the most frequently used treatment for the neonatal jaundice. However, recent papers report that phototherapy increased apoptosis in peripheral mononuclear leukocytes in vivo and in mouse lymphoma cell line in vitro. We have investigated the cytotoxicity of phototherapy on the small intestine of neonatal rat using conventional halogen-quartz device (conventional device) and blue light-emitting device (LED device) by measuring apoptotic cells. Four-day-old male Wistar rats were divided into three groups as follows: group 1, exposure to conventional device for 72 h; group 2, exposure to LED device for 72 h; and group 3, control (without phototherapy). After light exposure, the small intestine was examined for apoptosis. Apoptotic cells were detected by the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay, by immunohistochemistry for caspase-3 and by transmission electron microscopy. The proportion of positive cells by the TUNEL method in the epithelium of the small intestine was 6.2, 3.1 and 1.7% in the conventional device group, the LED device group and the control group, respectively. The apoptotic cells of the conventional device group is significantly higher than the LED device group (P < 0.01) and that of the LED device group was higher than that of the control group (P < 0.05). We suspected that phototherapy induced apoptosis in neonatal small intestine and the conventional device introduces more apoptosis than the LED device.