Volumetric changes in the kidney of rats following administration of Methadone and Bupronorphin by Cavalier's method

Methadone and buprenorphine are agonist and partial agonist of opioid receptors respectively. Opiates have side effects on various organs specially kidneys. In this study, effects of buprenorphine and methadone on volumetric changes of male rat kidney were investigated. In this experimental study, 15 male Wistar rats each weighing 250±15 gr were selected and randomly were divided into three groups (n=5). The first group received 0.5 mg/kg/day methadone and second group received 30 ng/kg/day buprenorphine, intraperitoneally for 15 days. The third group (control) received normal saline injection. After the last injection, the animals were anaesthetized, and the right kidney removed. Then suprarenal gland and renal capsule were separated and the kidneys were fixed in 7% buffered formalin solution for 72 hours. The specimens were embedded in 3.5% agar and 1mm coronal slices were prepared by means of a tissue slicer. Afterward using Cavalier’s point counting method, the volumes of the kidneys were calculated. Comparison between the groups performed using nonparametric statistical test of Kruskal-Wallis. P<0.05 was taken as the significant level. Mean volume of kidney (mm3) in methadone treatment, buprenorphine and control group were 602.4±44.8, 566.4±8.4 and 566.4±16.3, respectively. Comparison of these groups using Kruskal-Wallis statistical test showed that there were not any significant differences in kidney volume between the 3 groups (P>0.05). Methadone and buprenorphine during this period of time and with this dosage had not any significant effects on volumetric changes of kidney; although, relative increase in the volume of kidney in methadone group in comparison to buprenorphine and control groups may reflect primitive pathologic changes of kidney due to this opiate.