SUB-ACUTE ORAL TOXICITY OF TRANSFORMER MINERAL OIL IN WISTAR RATS

Abstract

There is an increasing trend in Kenya where local deep frying food-vendors use cooking oil blended with transformer mineral oil (TMO) in preparing edible products despite the scant knowledge on possible toxic effects of TMO. This study used a rat model to investigate possible sub-acute oral toxicity of TMO. Forty albino male and female Wistar rats of 6-8 weeks old were randomly distributed into 4 groups of ten animals (five of either sex): Control group were fed on corn oil only (COC, 200μl), low dose heated TMO (HLD-TMO, 50mg/kg bwt), high dose heated TMO (HHD-TMO, 500mg/kg bwt), and high dose unheated TMO (UHD-TMO, 500mg/kg bwt) groups in corn oil. The oral exposure was done by oral gavage once daily for 28 days. Physical observations of rats were done daily while changes in body weight were determined weekly. A full hemogram was conducted to determine haematological changes. Serum levels of Alanine transaminase (ALT), total protein (TP), globulin (GLOB), and albumin (ALB) were indicators of liver toxicity while creatinine (CRE) and urea levels were indicators of kidney toxicity. Malondialdehyde (MDA) levels, an index of lipid peroxidation, were measured in liver tissues using Thiobarbituric Acid Reactive Substances (TBARS) method. Tissues of liver, kidney, and small intestines were examined for histological changes. Data obtained was analysed statistically using student’s t test and Analysis of Variance (p< 0.05). Significant increase in red blood cells and haemoglobin levels were observed in HHD-TMO females and UHD-TMO males respectively as compared to the control. The HHD-TMO and UHD-TMO male rats showed significant decrease in ALT levels relative to the control. TP and ALB of the HHD-TMO females showed a significant decrease from the COC. The UHD-TMO female animals showed a significant decline in urea levels in comparison to the control. The HHD-TMO males and UHD-TMO males and females showed a significant increase in MDA levels relative to the control. For histopathology, rats in HHD-TMO group had a liver with bile duct proliferation; the female HLD-TMO and UHD-TMO animals showed liver with focal areas of periportal chronic inflammation; the rats in HHD-TMO group had kidneys with mild chronic inflammation; and the rats in HHD-TMO and UHD-TMO groups showed small intestines with chronic inflammation. In conclusion, sub-acute oral administration of TMO induced oxidative stress and varied degrees of toxicities among the various tissues of male and female rats. However, further studies are required to determine other toxicities.