Subchronic Toxicity of Mineral Oil Saturated Hydrocarbons (MOSH) in Relation to Its Carbon Number Range and Gender of Fischer F344 Rats

In this work, the paraffin oil was first molecularly distilled into two mineral oil saturated hydrocarbons (MOSH) subfractions with their main carbon number range of C20–30 (84.58%) and C30–50 (89.65%), which were determined using a liquid chromatography–gas chromatography–flame ionization detector (LC-GC-FID) technique. Then, both female and male Fischer 344 (F344) rats were fed with the diets containing one of these two MOSH subfractions at the low (1.5 g/kg) or high dose (15 g/kg) for 6 months. It was found that the exposure of MOSH C20–30 subfraction could result in a significant increase of spleen weight index (4.64 ± 0.18 mg/g for female and 3.79 ± 0.31 mg/g for male rats) (P < 0.05), and irregular shape of white medulla, and the macrophage infiltration in mesenteric lymph node for both female and male rats, especially for the 15 g/kg MOSH C20–30-fed rats. Meanwhile, both MOSH C20–30 and C30–50 subfraction promoted inflammation and oxidative stress and had a negative effect on the immune function in both female and male rats. The metabolomics results further supported these observations, and indicated the down-regulation of cysteine and methionine metabolism, and glutathione metabolism pathway in female and male rats, respectively.