Effects of Aluminum Trichloride on Structure and Function of Kidney in Chickens

Zhang Ji-hong,Luo Ji-long,Yu Hong-xiang,Bai Chong-sheng,Han Yan-fei,Xia Shi-liang,and Li Yan-fei

College of Veterinary Medicine,Northeast Agricultural University,Harbin 150030,China

Introduction

Aluminum (Al) is a kind of toxic element.When organism ingested excessive Al,Al would accumulate in the body,and exert toxic effects on the brain,heart,liver,kidney,etc (Scancar and Milacic,2006).Kidney has the ability to eliminate Al in the body under normal circumstances.Long-term or abundant Al ingestion will exert toxic effects and injure structure of kidney,because too much Al is accumulated in kidney that don't eliminate all of it.Höhr et al.(1989) showed that the ability of kidney to excrete Al in rats decreased,and the accumulation of Al in the body was obvious increasing.Dlugaszek et al.(2000) found that Al accumulated in the kidney of mice and exerted toxic effects.At present,effects of Al on kidney in chickens have not been reported yet.In this experiment,sub-chronic Al intoxication chickens were established to explore the effects of Al exposure on the renal structure and the function in chickens.

Materials and Methods

Materials

99% aluminum trichloride (AlCl3) crystal,0.25% trypsin and kits of creatinine (Cr) and blood urea nitrogen (BUN) contents were provided by Nanjing Jiancheng Bioengineering Research Institution (China).

Animals and treatments

A total of 80 healthy,one-day-old,ISA chickens (half male and half female) with a mean birth weight,were used in the experiment.All the chickens were acclimatized for 1 week before the experiment.They were randomly divided into four groups (20 chickens per group): control group (GC),low dose group (GL),middle dose group (GM) and high dose group (GH).The experimental group chickens were given 18.31,27.47 and 36.62 mg • kg-1• d-1Al3+in form of autoclaved AlCl3aqueous solution by peritoneal injection respectively,and the chickens in GC were injected with the same volume physiological saline at 0.2 mL each chicken.Each group was fed respectively in wooden cages and all of the tools did not contain Al.All of the chickens were freely accessed to food,water and a standard diet for up to 60 days.

Sample collection and treatment

Chickens in each group were sacrificed by picking blood from the heart at the end of Al exposure,then the blood were separated to obtain serum,kidney tissues were made into 1 cm×1 cm×1 cm and then immobilized in 10% formalin phosphate buffer.

Detection of Al levels in serum and kidney

1 mL serum and 1.0 g kidney were digested and then the levels of Al were measured with atomic absorption spectrophotometer by using the method of airacetylene flame (Bohrer et al.,2008).

Observation of kidney histopathology

Routine tissue paraffin sections were made from kidney,and the renal structure was observed and photos were taken by haematoxylin-eosin-stained under optical microscope.

Detection of Cr and BUN contents

Cr and BUN contents were detected strictly according to the kit instruction.

Statistical analysis

All the results were expressed as mean±standard deviation (SD).SPSS 13.0 software (SPSS Inc.,Chicago,IL,USA) was used for one-factor analysis of variance to compare the difference between the experimental group and GC.

Results

Levels of Al in serum and kidney

The Al content in Al exposure group was significantly higher than that in control group (P＜0.01) and increased with the increase of Al exposure dose.There was an AlCl3-dose depended manner (Table 1).

Effects of Al exposure on Cr and BUN contents in serum of chickens

There was no significant difference except the content of Cr between GL and GC.While the contents of Cr and BUN in other groups were significantly higher than those in GC (P＜0.05;P＜0.01) and increased with the increase of Al exposure dose.There was an AlCl3-dose depended manner (Table 2).

Table1 Contents of Al in serum and kidney (n=20)

Effects of Al exposure on histopathology of kidney in chickens

Under optical microscope,in GC,acinus renis,nephric tubule and proximal convoluted tubule possessed complete structure and lined up in order (Fig.1).In GL,the volume of acinus renis swelled mildly (Fig.2).In GM,the volume of acinus renis swelled,nephric tubule mildly water degenerated (Fig.3).In GH,the volume of acinu renis swelled,cell number of acinus renis increased,and nephric tubule water degenerated (Fig.4).

Table2 Contents of CR and BUN in serum (n=20)

Fig.1 Kidney in GC (×40)

Fig.2 Kidney in GL (×40)

Fig.3 Kidney in GM (×40)

Fig.4 Kidney in GH (×40)

Discussion

At present,Al poisoning animal models were established through peritoneal injection,subcutaneous injection,feeding feeds of Al-containing and drinking solution of Al-containing.It's difficult to get the exact dose of Al exposure through feeds or drinking water.The methods of peritoneal injection and subcutaneous injection can precisely control the dose of Al exposure,and peritoneal injection is more beneficial to the absorption than subcutaneous injection.So we established Al intoxication chickens with peritoneal injection in this experiment.

Kidney is a significant excretion organ in body.When kidney is aggressed by extraneous poisons and other negative factors,its structure is damaged in different degrees,and that would block the excretion of poison and metabolic waste,and disorder the metabolic of body.Al is also mainly excreted by the kidney.When absorption Al levels overload the excretion ability of Al in kidney,Al will accumulate in the kidney and induce toxic effects.Liu et al.(2002) found that the level of Al in kidney tissue significantly increased with the increase of Al dose (P＜0.01) after different concentrations of Al potassium sulfate were added to the feed of rabbits for 8 weeks.In this experiment,the Al levels in Al-treated chickens were significantly higher in serum and kidney than those in GC (P＜0.05;P＜0.01),and increased in an Al-dose dependent manner.It showed long-term Al exposure induced Al accumulation in kidney of chickens.

Long-term Al exposure damaged the pathological structure of kidney in rats (Yoshihito et al.,1984;Somova et al.,1997),and caused nephric tubule cloudy swell,blood capillary engorge swell and hyperemia and proximal convoluted tubule epithelium cell swell under optical microscope (Zhuo,2008;Yao,2006).This experiment showed acinus renis,renal tubule and proximal convoluted tubule had completed structure and lined up in order in GC,and in GL acinus renis swelled mildly and there were no apparent pathological changes in nephric tubule and proximal convoluted tubule,while in GM and GH,acinus renis swelled,cell numbers of acinus renis increased,acinus tubule cloudy swelled and proximal convoluted tubule epithelial cell swelled.It indicated that Al exposure damaged the structure of kidney in chickens.

Cr and BUN contents are generally applied for reflecting injured degrees of renal function.The concentration of Cr in serum depends on the ability of glomerulus filtration under exogenous.When renal parenchyma damaged,the filtration rate of glomerulus dropped to the critical point and the Cr concentration would rise sharply.Urea is the protein terminal small molecule metabolites in body.The concentration of urea in serum depends on excretion capacity of kidney when food intake and catabolism of body are stable.El-Demerdash (2004) discovered that the contents of urea and Cr in serum increased when rats were orally exposed to AlCl3for a month.Zhuo (2008) showed that the content of BUN in serum of Al exposure group was significantly higher than that in the control group and the Cr content did not have obvious difference after AlCl3exposure 3 weeks via filling stomach.This study showed that the content of BUN in GL increased (P＜0.05),but the content of Cr had no obvious difference (P＞0.05),which maybe relate with high degradation of protein in body after Al exposure.And the contents of Cr and BUN in GM and GH both increased (P＜0.01).It indicated that long-term Al exposure induced dysfunction of kidney in chickens.

In conclusion,the concentrations of Cr and BUN increased,and the histopathology of kidney was impaired in Al exposure chickens,which indicated that Al exposure injured the renal structure and function.

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