Prostaglandins, Leukotrienes and Essential Fatty Acids 72 (2005) 373–378 Short-term changes in prostacyclin secretory profile of irradiated rat cervical spinal cord Alireza Shirazi a , Seied Rabie Mahdavi a , Bagher Minaee b , Alireza Nikoofar c , Ebrahim Azizi d,Ã a Department of Medical Physics, Tehran University of Medical Sciences (TUMS), Tehran, Iran b Department of Anatomy and Histology, Faculty of Medicine, Tehran University of Medical Sciences (TUMS), Tehran, Iran c Faculty of Medicine, Iran University of Medical Sciences, Tehran University of Medical Sciences (TUMS), Tehran, Iran d Molecular Research Laboratory, Department of Pharmacology and Toxicology, Faculty of Pharmacy, Tehran University of Medical Sciences (TUMS), Tehran, Iran Received 17 August 2004; accepted 2 February 2005 Abstract Prostaglandins changes in radiation myelopathy (RM) have been previously reported. In the present study, we decided to determine the profile of Prostacyclin (PGI2) content in irradiated rat cervical cord. Wistar rats were irradiated with doses of 2,4,6,15,25 and 30 Gy of X-rays. After 24 h, 2 and 13 weeks post-irradiation, samples of spinal cord were prepared for evaluation of PGI2 and histopathologic changes. Prostacyclin content was determined by quantification of 6-keto-prostaglandin-F1a (prostacyclin major metabolite). Irradiated segments of spinal cord were stained routinely for histological studies. Results of irradiated were compared to control groups. Average ratio values of 6-keto-PG-F1a for doses of 2–30 Gy were between 67.5% and 107%, 65.41% and 100.54%, and 62.20% and 98.89% for 24h, 2 and 13 weeks post-irradiation, respectively. Histopathological studies showed marked gliosis and vascularities in irradiated specimens. PGI2 bimodal secretory profile was observed along with histopathological changes in this study. Our results can further emphasize on the role of PGI2 in RM. r 2005 Elsevier Ltd. All rights reserved. 1. Introduction Myelopathy is a serious and not rare complication of cancer and cancer treatment. Myelopathies may be induced through external pressure on cord, intramedul- lary metastasis or treatment toxicities associated with radiation therapy alone or in combination with other treatment methods. Radiation myelopathy (RM) in patients following radiotherapy made it the subject of vast clinical and radiobiological studies because it may not be diagnosed from the associated symptoms alone. Therefore, it seems there is a long way to understand the basic concept of mechanisms in the development of RM [1–4]. Dose–response curves for treatment of malignancies profoundly show a strict margin between virtual 100% tumoricidal dose and neurotoxicity occurrence in spinal cord as a normal tissue complication [2]. It was shown that single dose of 35 Gy X-ray to spinal cord can cause limb paralysis in rat models with a latency of 19.070.3 weeks [5]. In conventional radiotherapy incidence of RM after doses of 57–61Gy is 5% with a good approximation. Analysis of patients developing RM demonstrated that the upper limit of tolerance for a X5cm length of the cervical spine was 50Gy (25 fractionates/35 days). The mostly used dose limit for spinal cord is 45Gy in 22–25 fractions and this is considered as tolerance dose. Yet, due to morbidity of RM, spinal cord dose should always be kept under tolerance limit [6–10]. Radiobiologically, it was reported that linear quad- ratic (LQ) model does not provide a satisfactory ARTICLE IN PRESS www.elsevier.com/locate/plefa 0952-3278/$-see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.plefa.2005.02.003 Ã Corresponding author. Tel./fax: +98216959100. E-mail address: aziziebr@sina.tums.ac.ir (E. Azizi).