Comparative pathologic and stereologic study of respiratory system in mice following administration of 3-methyl indole dissolved in propylene glycol and cremophor EL and LD50 determination

Shahbazfar, Amir AliMohammadpour, HemnRajabi, Nastaran AhangaranAsmand, Mohsen

Background: 3-Methyl indole (Skatole, 3-MI) is produced by microfloral fermentation of tryptophan in rumen and production of that has relation with the onset of respiratory problems in cattle. The aim of this study was to compare complications of 3-MI dissolved in two solvents, Cremophor and Propylene Glycol on BALB/c mice by histopathologic and stereologic studies. Materials, Methods & Results: Female Balb/C mice 56 days of age (23 - 27 g) were divided into 13 groups of eight and had access to food and water ad libitum. Mice were housed in plastic cages (4 per cage) with wire bar lids on bedding of sawdust in an air-conditioned room with 12 h light: dark cycles. After a 7-day acclimation period, for 5 groups, Mice were injected with 400, 500, 600, 700 and 800 mg/kg from solution of 3-MI in propylene glycol and similarly for 5 other groups with Cremophor. As well as 2 groups were injected with Propylene glycol and Cremophor with the dosage that is necessary for solving the highest dose of 3-MI. One group received normal saline with the volume equal with Cremophor (drug vehicle) group. Briefly, 125 mg of 3-MI was dissolved per mL of sterile filtered Propylene glycol and 30 mg of 3-MI was dissolved per mL of sterile filtered Cremophor. Once injected intra peritoneally, mice were monitored 3-4 h for external reaction signs from the injection. LD50 was determined 610.16 mg/kg 3-Methylindole and 687.5 mg/kg 3-Methylindole dissolved in Propylene glycol and Cremophor respectively with linear regression. Increase in respiration rate, tachypnea and shallow respiration was observed in clinical examination. In necropsy, alveolar and bronchial hyperemia was significant in lungs. Some superficial wounds were observed in upper respiratory airways. Trachea and Hungarian airways were severely hyperemic. There were some debris’s in airways canals. We couldn’t find any lesion in other organs. Histopathology showed noticeable alveolar edema and emphysema, type I pneumocytes necrosis, Slight endothelial lesions, rare degeneration of type II pneumocytes and raised nutrophil infiltration around vessels were observed in higher dosages of both groups. Moderate interstitial edema, hyperemia and increase of alveolar macrophages were observed too. Increase of lymphocytes was noticed after the dose 600 mg/kg moderately on a dose dependent manner. There was a Hyaline membrane in the wall of air sacs. Endothelial capillary damage in Cremophor dissolved 3-MI groups were slightly lower. Although damage to the vessels was not that much progressed in both groups. Stereologic study of type II pneumocytes showed a significant increase in the percentage of them in alveoli of treatment groups in a dose dependent manner compare to control and drug vehicle groups. At the highest dose (800 mg/kg) the group with Propylene glycol as solvent had significant difference with Cremophor dissolved 3-Methyl indole group and epithelialization was more severe in that. Bronchiole injuries raised in a dose dependent manner in both treatment groups. Discussion: The results of this research indicate that intraperitoneal infusion of 3-MI dissolved in Propylene glycol and Cremophor cause noticeable changes in the respiratory systems of mice. Effects of 3-MI in Propylene glycol is more severe than 3-MI dissolved in Cremophor but type of the lesions is not different. Bronchiolar lesions were moderate compare to the effects of 3-MI in some other animals. Severity of vascular lesions in Propylene glycol dissolved 3-MI was greater than groups that received the Cremophor dissolved 3-MI. Although the vascular injuries were not that much noticeable at all.(AU)

1. emphysema
2. LD50
3. pulmonary edema
4. Balb/c mice
5. 3-Methylindole