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The effect of surgery and swimming chronic stresses on plasma leptin concentration in adult male rats.

INTRODUCTION

Several hormones are secreted from adipose tissue, and leptin is one of them. Leptin is a protein hormone that regulates body weight and metabolism, and it has a main role in energy consumption and reproductive function [1]. Also, in lower levels leptin is secreted by the cells in gastric epithelium tissue, placenta, skeletal muscle, liver, ovary, bone marrow, hypothalamus, pituitary and mammary gland epithelial cells [6-2]. Stress activates the sympathetic system [3,7]. Some studies in the absence of stress show that epinephrine and norepinephrine have an inhibitory effect on leptin secretion [8,9]. This inhibitory effect has not been reported by some researchers [10]. Stress also causes activation of the hypothalamic--pituitary--adrenal (HPA axis) [3,7]. In fact, this axis in response to the stress plays an important role in the adaptation to stressful conditions. It has recently been shown that adipose tissue, by secretion of leptin, plays a role in the stress responses. Glucocorticoids and possibly synthesis ACTH stimulate leptin secretion, and reversely leptin effects activation of adrenal glands [11,12]. In relation to the effect of axis of the hypothalamic--pituitary--adrenal on the secretion of leptin, the results are different. In one study, injection of dexamethasone increases leptin serum concentrations in dogs [13]. In another study, following the removal of adrenal glands in the non-stress conditions, ACTH levels increase, and so corticosterone serum levels and leptin secretion decreased. In this study, giving corticosterone to the rats of the sham group causes significant decrease of ACTH and increase of leptin serum levels. The results showed that ACTH, unlike glucocorticoids has an inhibitory effect on leptin secretion [14]. In another study it was indicated that injection of leptin inhibits the secretion of ACTH and corticosterone in rats that have been exposed to restraint stress for four hours [15]. Given that most studies related to pituitary--adrenal axis on the secretion of leptin in non-stress conditions have been investigated, the present study investigates the role of this axis on leptin concentration in stress conditions that increase activation of this axis.

Methods:

In the present experimental study, 48 Sprague-Dawley male rats weighing (200-220 g) were used. The animals were kept in the Animal House at Jahrom Medical University in standard conditions (12 hours light-12 hours dark at 22 [+ or -] 2 [degrees]C). The animals were randomly divided into 6 groups as follows:

1) First group: Healthy male rats without swimming stress

2) Second group: Healthy male rats with swimming stress

3) Third group: Surgery male rats without swimming stress

4) Fourth group: Surgery male rats with swimming stress

5) Fifth group: Adrenalectomized rats without swimming stress

6) Sixth group: Adrenalectomized rats with swimming stress

Adrenal glands removal procedure: After anesthetizing with ketamine and xylazine animals and shaving the area, two vertical cuts were made using a surgical blade, with a length of 1 cm behind the back between the first and third vertebrate. The skin and underlying muscle tissue were carefully pushed and again after removal of the adrenal glands, muscle and skin tissues were sewn with a needle and suture number 4. Animals were injected intraperitoneally with a dose of antibiotic at a concentration of 120mg/kg. Normal saline was instilled in the water container of animals in this group during experiment rather than water.

Surgical Induction method: According to the above procedure, rats were anesthetized and two vertical incisions were made behind their back and the muscles set aside, and again the muscles and skin were sutured. A single dose of antibiotic was injected intraperitoneally to these animals as well.

Method of induction of swimming chronic stress: The animals were placed for seven consecutive days, each day for ten minutes (between 10am-12) in a water container with a volume of 20 liters at a temperature of 25[degrees]C. Then the animals were removed from water and were dried with a clean towel. However, in surgical and adrenalectomized groups swimming chronic stress period began from the eighth day after the end of recovery period.

Method of production of plasma and measurement leptin concentration: After ending seven day stress periods (eighth day after stress began), blood samples were collected directly from rats heart using 2 ml syringe. After preparation of plasma the obtained samples were maintained at the temperature of -60[degrees]C. To determine concentrations of leptin, ELISA kit was used (Biovendor Co. Czech--Oslovakia Lot : RD-1698 S2).

Statistical analysis:

For data analysis, SPSS version 13 software and ANOVA was used to compare groups. The value of P < 0.05 was considered as statistically significant level. The mean and standard deviation data were calculated.

Results:

As Table 1 shows, swimming and surgical stresses cause significant increase of leptin concentrations (P < 0.001) but adrenalectomy causes significant decrease of leptin concentration (P < 0.001). Between the sham and adrenalectomy groups, there was a significant difference of plasma leptin concentration (P < 0.001). In adrenalectomy group and surgical stress, swimming stress causes no significant change in leptin concentration (P = 0.82, P = 0.74) (Table 1).

Discussion and conclusion:

The results showed that after swimming chronic stress, plasma leptin concentration was significantly increased. Perelo et al's study in 2005 showed that in male rats, following social stress for 30 days, corticosterone and plasma leptin concentrations were increased [16]. In another study, 6 hours after Immersion restraint stress, plasma leptin concentration was significantly increased [17]. In order to investigate the relationship between the hypothalamus--pituitary--adrenal axis and secretion of leptin, adrenal glands were removed and the effect of adrenalectomy on leptin concentrations was measured. As Table 1 shows, following adrenalectomy, leptin concentration was significantly decreased. It seems that the stress by activation of hypothalamic--pituitary--adrenal axis causes increase of glucocorticoid secretion and finally leads to increase of leptin secretion. In adrenalectomy state, because of the stimulatory effect glucocorticoid is lost, resulting in a decrease in leptin serum levels [18,19]. Increase of Plasma ACTH concentrations in the stress state can also act as a stimulus and cause the secretion of leptin [20]. In this study, surgery stress alone can cause an increase of leptin plasma concentration. In a study conducted on 22 patients, it was determined that following surgery, leptin concentration increased from 6 [+ or -] 1/9 ng/ml to 9/9 [+ or -] 2/7 ng/ml [18]. It seems that surgery alone will probably act as a stressful factor and cause activation of the hypothalamus--pituitary--adrenal axis. However, in surgery group with swimming stress, swimming stress caused no significant change in leptin concentration compared to sham group (P = 0.82). This state is probably due to adaptation phenomenon of the body against stressful factors [20-25].

ARTICLE INFO

Article history:

Received 22 October 2013

Received in revised form 14

January 2014

Accepted 20 January 2014

Available online 15 February 2014

REFERENCES

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(1, 2) Kargar Jahromi Hossein, (3) Bathaee Seyed Hamid, (4) Saberi Roza, (5) Khodaparast Zahra, (6) Farzam Mohammad, (6) Rahmanian Elham

(1) Zoonoses research center, Jahrom University of Medical Sciences, Jahrom, Iran.

(2) Young Researchers Club Elite, Jahrom Branch, Islamic Azad University, Jahrom, Iran.

(3) Institution of Supreme Education and Industry of Maragheh, Iran.

(4) Department of Biology, Islamic Azad University, Jahrom, Fars, Iran.

(5) Department of Biology, Islamic Azad University, Arsanjan, Fars, Iran.

(6) Department of Anatomy and Embryology, International Branch, Shiraz University, Shiraz, Iran.

Corresponding Author: Hossein Kargar Jahromi, Jahrom University of Medical Sciences, Jahrom, Iran.

Tel: +989361554955 E-mail: hossein.kargarjahromy@yahoo.com
Table 1: All groups were compared in terms of leptin concentration.

Adrenalectomy          Adrenalectomy          Surgical stress
with swimming                                 with swimming
stress                                        stress

51.33 [+ or -] 5.52    52.69 [+ or -] 11.56   144.87 [+ or -] 10.62

Adrenalectomy          Surgical stress        Normal with
with swimming                                 swimming stress
stress

51.33 [+ or -] 5.52    146.80 [+ or -] 4.71   167.70 [+ or -] 13.70

Adrenalectomy          Normal                 Attribute
with swimming                                 group
stress

51.33 [+ or -] 5.52    129.10 [+ or -] 5.85   Leptin
                                              Pg/ml
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Article Details
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Author:Hossein, Kargar Jahromi; Hamid, Bathaee Seyed; Roza, Saberi; Zahra, Khodaparast; Mohammad, Farzam; E
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:7IRAN
Date:Dec 1, 2013
Words:1966
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