Distinct Response of Lactating and Nonlactating Rats Exposed to Inorganic Mercury on Hepatic δ-Aminolevulinic Acid Dehydratase Activity

Abstract

This study investigated if lactating and nonlactating rats presented differences in relation to hepatic sensitivity to HgCl2 and the potential preventive role of ZnCl2. Lactating (days 3-12 of lactation) and nonlactating rats received 27 mg/kg ZnCl2 for five consecutive days and 5 mg/kg HgCl2 for five subsequent days. Lactating and nonlactating rats exposed to HgCl2 presented a decrease in food intake, a decrease in plasma alanine aminotransferase (ALT), and an increase in hepatic Hg levels when compared to the control group. Only lactating rats exposed to HgCl2 presented an increase in hepatic δ-aminolevulinic acid dehydratase activity. On the other hand, only nonlactating rats exposed to HgCl2 presented an increase in plasma aspartate aminotransferase (AST). ZnCl2 pre-exposure partially protected the increase in plasma AST activity presented by nonlactating rats and potentiated the liver Hg accumulation in lactating rats. Pups from the Sal-Hg and Zn-Hg groups showed a decrease in absolute liver weight and an increase in liver Hg levels. Summarizing, this study demonstrated that lactating rats presented distinct biochemical responses compared to nonlactating rats exposed to HgCl2 when hepatic parameters were evaluated.

Zinc and N-acetylcysteine modify mercury distribution and promote increase in hepatic metallothionein levels

“…Inorganic mercury also affects liver, blood, intestine, thyroid and testicles [3,4]. In fact, recent studies have demonstrated that animals exposed to mercury chloride (HgCl 2 ) (5 mg/kg) present renal [5][6][7][8], hepatic [9][10][11][12], testicular [13], behavioral [14,15] and cardiovascular [16] alterations.…”

Acute mercury exposition of virgin, pregnant, and lactating rats: Histopathological kidney and liver evaluations

“…The brain total thiol (TSH) levels were determined as previously described by Ellman () and meantime for the nonprotein thiol (NPSH) evaluation, 200 µL of the protein supernatant fraction were precipitated with 200 µL of 4% trichloroacetic acid (v/v) by centrifugation (1050 × g for 10 min), as previously described by Oliveira et al (). The colorimetric analyses were carried out in 1M phosphate buffer (pH 7.4).…”

“…Toxicity of inorganic Hg can lead to disturb the pro‐oxidant or anti‐oxidant balance thereby inducing oxidative stress in kidney and liver following parenteral administration of Hg (Ansar and Iqbal ; Antune et al, Mahboob et al, ; Othman et al, ). The principal inorganic form (mercury chloride ‐ HgCl 2 ) is recognized to cause mainly nephrotoxicity (Franciscato et al, ; Moraes‐Silva et al, ; Oliveira et al, ; Roza et al, ) and also hepatotoxicity (Ansar and Iqbal ; Deng et al, ; Karapehlivan et al, ).…”

“…Oliveira et al () demonstrated that, during pregnancy, the exposition to low doses of HgCl 2 in drinking water causes a decrease in food intake and body weight gain in rats dams. Recently, it was suggested that virgin female rats are different from lactating dams in relation to HgCl 2 sensitivity (Favero A.M. et al, ; Oliveira C.S. et al, ) .…”

“…et al, ) . In fact, the perinatal period, is characterized by several important physiological and metabolic changes in all the body of mammals and this makes the pregnant and lactating dams respond differently when exposed to chemical substances, whether drugs or toxic agents (Cheung and Lafayette ; Cummings et al, ; Houpert et al, ; Oliveira et al, ; Sundberg et al, ; Tan and Tan, ). In addition to hormonal changes involved during pregnancy and lactation period, also some organs and systems, that are not directly involved in the development of the fetus, like urinary and digestive apparatus, are significantly altered.…”