Cytogenetic and Hormonal Alteration in Rats Exposed to Recommended "Safe Doses" of Spinosad and Malathion Insecticides

This study evaluated the cytogenetic and reproductive effects of spinosad and malathion on male albino rats. The insecticides were given daily, via oral route, in 60 repetitive doses equaled to Acceptable Daily Intake “ADI” (0.02 & 0.30 mg a.i.kg -1 b.w.), No Observed Adverse Effect Level “NOAEL” (9.00 & 29.00 mg a.i.kg -1 b.w.) and 1/100 LD50 (37.38 & 13.75 mg a.i.kg -1 b.w.) of spinosad and malathion respectively. Results of cytogenetic effects indicated that spinosad (37.38 mg a.i. kg -1 b.w.) and malathion (13.75 & 29.00 mg a.i.kg -1 b.w.) induced significant decrease in mitotic activity (MI %) and increased micronucleated polychromatic erythrocyte (MN %) in rat's bone marrow cells. The MN % recorded 0.36% in control rats, compared to 0.96% for spinosad at 37.38 mg a.i.kg -1 b.w. and 1.46 and 1.93% for malathion at 13.75 and 29.00 mg a.i.kg -1 b.w., respectively. Except the treatment with 0.02 mg a.i. kg -1 b.w. (ADI) of spinosad, the other tested doses of both insecticides showed significant increase in the percentage of chromosomal aberrations in rat's bone marrow cells. The percentage of chromosomal aberration (excluding gaps) recorded 0.66, 1.33 and 3.66% for spinosad at 0.02, 9.00 and 37.38 mg a.i. kg -1 b.w., respectively. In case of malathion, such values recorded 3.00, 6.33 and 6.66% at 0.30, 13.75 and 29.00 mg a.i.kg -1 b.w., respectively. The obtained cytogenetic effects occurred in a dose-dependent manner. After 45 days of treatment, testosterone concentration significantly decreased (P ≤ 0.05) at a dose levels of 9.00 and 37.38 mg a.i.kg -1 b.w. spinosad and 0.30 mg a.i. kg -1 b.w. malathion. At the other tested doses, malathion caused highly significant decrease (P ≤ 0.01) in testosterone concentration. Moreover, varieties of histopathological lesions were identified in the examined testes. The incidence and severity of these lesions appeared to increase with increasing dose and the most pronounced pathological changes were necrosis of spermatogonial cells, congest in blood vessels and exfoliation of necrotic cells within the somniferous lumen. The tested doses of both insecticides recorded observable significant decrease in the absolute testes weights and the lowest value (2.18 g) was resulted from malathion at the 1/100 LD50 (29.00 mg a.i. kg -1 b.w.). Except the treatment with 0.02 mg a.i. kg -1 of spinosad, the other tested doses of both insecticides showed significant decrease in body weight gains. Generally, cytogenetic and reproductive effects, as well as alteration in testosterone level, were observed in a dose-dependent manner and malathion exhibited more pronounced effect than spinosad.