The protective role of the opioid antagonist LY255582 in the management of high fat diet-induced obesity in adult male albino rats.

OBJECTIVES: The involvement of the opioid system in energy balance has been known for several decades but many questions remain unanswered. Therefore, this study was designed to investigate the effect of the non-selective opioid receptor antagonist (LY255582) on high fat diet (HFD)-induced obesity. METHODS: Twenty-four adult male albino rats were divided into 4 groups: Control, HFD non-treated, HFD+LY255582 treated during the first 4 weeks and Obese-LY255582- treated groups during the following 4 weeks after the induction of obesity. LY255582 (0.31 mg/kg, s.c.) was administrated daily with HFD feeding. Blood samples were collected for measurement of lipid profile, glucose, insulin, and leptin. Body weight, body mass index (BMI), and food intake were also measured. RESULTS: Consumption of HFD resulted in a significant increase in body weight, body mass index (BMI), glucose, insulin, leptin levels, and induced a state of dyslipideamia. Opioid antagonist LY255582 administration with HFD decreased food intake, body weight and BMI, in addition to the improvement of HFD related metabolic abnormalities (dyslipidemia and insulin resistance) during the dynamic phase of obesity development than in animals with already developed dietary obesity. CONCLUSION: The use of opioid antagonist may be a promising approach in treatment of HFD-induced obesity.

Effect of unilateral adrenalectomy on acute immobilization stress response in rats.

OBJECTIVES: The aim of the present study was to investigate the differential effect of unilateral adrenalectomy, right vs. left, in response to acute immobilization stress (IS) in rats. METHODS: Adult male rats were subjected to unilateral right or left adrenalectomy or sham operation (control). Two weeks later, the rats were sacrificed either immediately or 3 hours after IS exposure. Plasma samples were used for determination of catecholamines (CAs), adrenocorticotrophic hormone (ACTH), corticosterone (CORT), sodium, potassium, and glucose levels. After terminating the experiment, both or remaining adrenals were removed, weighed, and used for estimation of CAs and nitric oxide (NO) levels. RESULTS: Under basal conditions, either right or left adrenal kept all the tested parameters near to the control levels, except the adrenal weight and CAs content. These were significantly higher in the remaining right than left adrenal. However, the remaining right adrenal responded better to IS exposure than the remaining left one in the term of compensatory adrenal growth and plasma parameters which were all kept insignificantly different from those of IS intact group. CONCLUSION: Our data indicate that the adrenal glands may substitute each other under basal conditions. However, the right adrenal seems to be dominant during exposure to acute immobilization stress.

Biological variations in adrenal gland response to immobilization and glucoprivation stressors in rats.

OBJECTIVES: The aim of the present study was to investigate the potential variation in adrenal gland response to two different types of acute stressors, immobilization and glucoprivation. METHODS: Twenty-four adult male albino rats were randomly divided into three main groups (8 rats/group): a) control, i.e. non-stressed group, b) immobilized group (IS), and c) glucoprivated (GS) group. Plasma catecholamines (CAs), including epinephrine (E), norepinephrine (NE), dopamine (DA), adrenocorticotrophic hormone (ACTH), corticosterone (CORT), sodium, potassium, and glucose were measured. Adrenals weight, CAs levels, and nitric oxide (NO) content were also determined. RESULTS: Immobilized group of rats showed significantly higher plasma NE and DA levels along with a significantly lower adrenal NE content than GS group. On the other hand, GS group was associated with significantly higher plasma E, ACTH, CORT, glucose, and Na+ levels as well as higher adrenal DA and NO levels along with significantly lower plasma K+ levels and adrenal E content in comparison with IS group. CONCLUSION: Stress response is unique according to the nature of the stressor. Adrenal glands play a key role in this stress-induced differentiated response probably via modulation of its adreno-medullary and/or adrenocortical hormone levels in order to assign the body cope with different types of stress challenges during the life.

Effect of essential fatty acid deficiency on G-proteins, cAMP-dependent protein kinase activity and mucin secretion in the rat submandibular salivary glands.

Studies were conducted to determine whether beta-adrenergic cell signalling is altered in submandibular salivary glands (SMSG) is essential fatty acid (EFA) deficiency. Three groups of rats were fed diets which were deficient in EFA (EFAD), marginally deficient in EFA (MEFAD) or contained sufficient amount of EFA (Control). Rats were killed after 20 wk on diets, SMSG were dissected out and cyclic AMP-dependent protein kinase (PKA) activity was measured. The specific enzyme activities were higher in the homogenates and supernatant fractions of the gland from EFAD and MEFAD rats compared with the controls. The relative levels of guanine nucleotide-binding regulatory proteins (Gs and Gi) were also measured in the SMSG membranes of rats fed the 3 diets. The levels of Gs were significantly higher in the EFAD and MEFAD groups than in the controls. No significant differences were observed in the secretion of trichloroacetic acid-phosphotungstic acid (TCA-PTA) precipitable glycoproteins from the SMSG slices among the 3 dietary groups.