RESUMO
AIM: To investigate the time - effect relationship between the expression of rhodopsin and recoverin and photoreceptor damage induced by N - nethl - N -nitrosourea ( MNU) . METHODS: Thirty-six 7-week old Sprague-Dawley ( SD ) rats were intraperitoneally injected with MNU ( 60mg/kg ) and were put to death by dislocation of cervical vertebra 6, 12, 24h; 3, 7d after injection ( 6 per group) , respectively. As a control, six rats were injected with phosphate buffer saline (PBS) 5mL/kg and sacrificed on d3 after injection. The degree of photoreceptor apoptosis was detected by HE staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling ( TUNEL ) and transmission electron microscope ( TEM ) in the right eyes. The mRNA expressions of rhodopsin and recoverin were detected different time after injection by Western blot and immunohistochemical method in the left eyes. RESULTS:The dissolution of photoreceptor nucleus and apoptosis body were first perceived at 12h by TEM; most of cells at outer nuclear layer were presented positive reaction. The apoptotic index reached peak ( 29. 7% ±2.3%) at 24h which was coincided with the observation of TEM. The results of immunohistochemistry displayed that rhodopsin and recoverin were on a declining curve with time extension. Furthermore, the results of Western blot indicated that rhodopsin had dramatic decline at 6h after injection (P CONCLUSION:60mg/kg MNU intraperitoneally injection one - time may specifically induce photoreceptor apoptosis, The mechanism of down - regulation of rhodopsin and recoverin may be related to the selected apoptosis of photoreceptors.
