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.

The effect of ghrelin antagonist (D-Lys3) GHRP-6 on ovariectomy-induced obesity in adult female albino rats.

OBJECTIVE: We aimed to investigate the effect of ghrelin antagonist (D-Lys3) GHRP-6 on the treatment of ovariectomy-induced obesity as compared to hormone replacement therapy with estradiol. METHODS: Twenty eight rats were divided into four groups: control sham operated (C), ovariectomized non-treated (OVX), ovariectomized+estradiol-treated (OVX+E) groups, and ovariectomized+ghrelin antagonist-treated group (OVX+GA). Rats were allowed free water and commercial standard diet ad libitum for 5 weeks after surgery. Body mass index (BMI) was determined at the beginning and the end of the experiment. Rats were sacrificed by decapitation and blood samples were collected for measurements of serum lipid profile, insulin, and glucose levels. Gastrocolic omental fat (GCOF) was removed and weighed. RESULTS: Ovariectomy was accompanied with a significantly higher body weight, food intake, BMI, GCOF, serum total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), glucose, insulin, and homeostatic model assessment - insulin resistance (HOMA-IR), with a significant decrease in high density lipoprotein-cholesterol (HDL-C) and triglycerides (TGs) in comparison with C group. Estradiol reversed the ovariectomy-induced changes except that of TGs. Administration of ghrelin antagonist was effective in treating the ovariectomy-induced obesity as evidenced by normalization of body weight, food intake, BMI, and GCOF weight, serum levels of insulin, glucose, HOMA-IR, and HDL-C. The serum levels of TC, LDL-C and TGs were improved but did not reach the control values. CONCLUSION: Although estradiol succeeded in the prevention of almost all ovariectomy-induced disturbances, it had a potential cardiovascular risk due to a marked increase in serum TGs. Ghrelin antagonist was effective in ameliorating ovariectomy-induced obesity, so it may be used as a promising treatment for postmenopausal obesity, irrespective of hormonal replacement.

The effect of induction of endogenous CO by heme-oxygenase inducer, hemin versus heme-oxygenase blocker, zinc mesoporphyrin on gastric secretion and ulceration under different conditions in adult male albino rats.

Although its role and importance is less well studied, carbon monoxide (CO) has been identified as the second gasotransmitter in the GI tract. This study was performed to investigate the effect of modifying the endogenous CO production by altering heme oxygenase (HO) activity either by induction through hemin administration or inhibition by zinc mesoporphyrin administration on gastric secretion and ulceration induced by either cold restraint stress (CRS) or indomethacin (IND) treatment in adult male albino rats. Our results revealed that hemin significantly increased HO-1 levels with an increase in carboxyhemoglobin (COHb) level while zinc mesoporphyrin significantly decreased HO-1 levels with a decrease in COHb level in all groups. Hemin pretreatment significantly attenuated the gastric mucosal lesions induced by CRS and IND administration, which was accompanied by significant reduction in free and total acidity of gastric secretion, decreased proteolytic activity and marked attenuation of lipid peroxidation inspite of decreased NO and PGE2 levels. On the other hand, Inhibition of HO-1 activity by zinc mesoporphyrin prevented most of the effects caused by hemin administration except for its similar reduction in gastric mucosal NO and PGE2 levels. On conclusion, Hemin exerts a protective effect against CRS and IND-induced gastric ulcers possibly via inducing HO-1 and increasing endogenous production of CO (Tab. 2, Fig. 4, Ref. 75).

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.

Prostaglandin E2 production in submandibular salivary glands of rats in essential fatty acid deficiency.

Three groups of rats were fed an essential fatty acid (EFA)-deficient diet (EFAD), marginally EFA-deficient diet (MEFAD) or a control diet. Arachidonic acid levels in total phospholipids and the ex-vivo production of prostaglandin E2 (PGE2) in the presence of calcium ionophore were measured at 5 and 9 weeks in the submandibular salivary glands (SMSG). The arachidonic acid levels were significantly different among the 3 groups of rats fed the respective diets for 9 weeks. Ex-vivo PGE2 production was significantly decreased in the EFAD group but not in the MEFAD group as compared to the control group. The changes in fatty acid composition, arachidonic acid levels and ex-vivo production of PGE2 were reversed after 5 weeks of feeding the control diet to the EFAD or the MEFAD rats. Since arachidonic acid and PGE2 are involved in signal transduction pathways in the SMSG, an EFA deficiency is likely to modify these pathways.