Role of alpha-2 adrenergic receptors in anti-ulcer effect mechanism of estrogen and luteinising hormone on rats

The Role of Alpha-2 Adrenergic Receptors in Anti-ulcer Activity

Although peptic ulcer disease has long been recognized, the proposed mechanisms of its etiopathogenesis change every year. This review shows that gastric ulcers have a significant relationship with alpha-2 adrenergic receptors. The aggravating factors of gastric ulcer formation have been reported to act by blocking alpha-2 adrenergic receptors, whereas drugs possessing anti-ulcer activity have been shown to ensure gastric protection by stimulating the alpha-2 adrenergic receptors. The data derived from the literature indicate the likelihood that any drug or substance selectively stimulating the alpha-2 adrenergic receptors may possess anti-ulcer activity.

Effect of methylprednisolone on bone mineral density in rats with ovariectomy-induced bone loss and suppressed endogenous adrenaline levels by metyrosine

Objectives:

In this study, effect of methylprednisolone on bone mineral density (BMD) was investigated in rats with overiectomy induced bone lose and suppressed endogenous adrenalin levels, and compared to alendronate.

Materials and Methods:

Severity of bone loss in the examined material (femur bones) was evaluated by BMD measurement.

Results:

The group with the highest BMD value was metyrosinemetyrosine + methylprednisolone combination (0.151 g/cm²), while that with the lowest BMD was methylprednisolone (0.123 g/cm²). Alendronate was effective only when used alone in ovariectomized rats (0.144 g/cm²), but not when used in combination with methylprednisolone (0.124 g/cm²). In the ovariectomized rat group which received only metyrosine, BMD value was statistically indifferent from ovariectomized control group.

Conclusions:

Methylprednisolone protected bone loss in rats with suppressed adrenaline levels because of metyrosinemetyrosine.

An investigation about the inhibition of acute ischemia/reperfusion damage by dexmedetomidine in rat ovarian tissue

Reperfusion has always been "the emergency intervention" to ischemic tissue. For a given period of time, tissue injury due to ischemia and reperfusion is more serious than injury due to ischemia only. Groups were as: Group 1: 25 µg/kg dexmedetomidine + ischemia/reperfusion group. Group 2: 10 mg/kg yohimbine +25 µg/kg dexmedetomidine + ischemia/reperfusion group. Group 3: Ischemia/reperfusion (control) group. Group 4: Healthy rats. Rat ovaries were exposed to a 3-hour ischemia and then reperfusion ensured for 2 hours. After ischemia/reperfusion, total glutathione, malondialdehyde, 8-hydroxyguanine levels and histopathological investigation were studied. The highest total glutathione and the lowest malondialdehyde and DNA damage levels were determined in dexmedetomidine group when compared to control group. The difference between yohimbine + dexmedetomidine and the control group was insignificant. Dexmedetomidine protects the ovarian tissue of the rat from I/R injury. It is hypothesized that this protective effect of dexmedetomidine is mediated by the α-2 adrenergic receptors. Dexmedetomidine could be useful for attenuation of tissue damage after I/R and prevention of I/R-related complications.

Protection of estrogen in portal hypertension gastropathy: an experimental model

CONTEXT

Portal hypertension is a complication secondary to cirrhosis that is characterized by increased blood flow and/or vascular resistance in the portal system, causing the appearance of a hyperdynamic collateral circulation. Partial portal vein ligation is an experimental model used in rats to study the pathophysiological mechanisms involved in pre-hepatic portal hypertension. Estrogen E2 is an antioxidant molecule with various physiological actions.

OBJECTIVES

To evaluate the antioxidant activity of endogenous estrogen in an experimental model of partial portal vein ligation by comparing intact with castrated rats.

METHODS

Twenty Wistar rats, weighing on average 250 g were used and divided into four groups: sham-operated (SO); intact (I) with partial portal vein ligation (I + PPVL), castrated (C) and castrated with partial ligation of the vein (C + PPVL). Day 1: castration or sham-operation; day 7, PPVL surgery; on day 15 post-PPVL, portal pressure in the mesenteric vein of rats was measured on polygraph Letica. Lipid peroxidation in the stomach was assessed using the technique of thiobarbituric acid reactive substances and activity of antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase. Statistical analysis was done with ANOVA - Student-Newman-Keuls (mean ± SE), and P<0.05 was considered as significant.

RESULTS

Portal pressure was significantly increased in C + PPVL as compared to the other groups. There was no significant difference in the group of intact rats. TBARS showed significant damage in C and C + PPVL in relation to others. Antioxidant enzymes were significantly increased in the castrated rats with subsequent PPVL as compared to the other groups.

CONCLUSION

We suggest that estrogen E2 plays a protective role in intact compared with castrated rats because it presents hydrophenolic radicals in its molecule, thus acting as an antioxidant in this experimental model.

The protective effects of metyrosine, lacidipine, clonidine, and moxonidine on kidney damage induced by unilateral ureteral obstruction in rats

PURPOSE

To investigate the effects of metyrosine, lacidipine, clonidine, and moxonidine on the renal damage in rats with unilateral ureteral ligation by examining the histological evidence of parenchymal damage and tubular dilatation, as well as biochemical changes indicating cell membrane damage and DNA oxidation.

METHODS

Thirty-six albino Wistar rats were randomly divided into six equal groups: a healthy (intact) group, a unilateral ureteral ligation (control) group, and four drug treatment groups given metyrosine (50 mg/kg), lacidipine (2 mg/kg), clonidine (0.075 mg/kg), or moxonidine (0.2 mg/kg), respectively, for 10 days. The latter five groups underwent ligation of the left ureter. Ten days after the operation, we removed both kidneys from each rat in the control and drug treatment groups for renal pathological and biochemical [malondialdehyde (MDA), total glutathione, 8-hydroxy-2-deoxyguanine (8-OH-Gua)] examinations. Spectrophotometric assays were used to detect the malondialdehyde and total glutathione levels of the renal tissue. High-performance liquid chromatography was used to measure the 8-hydroxy-2-deoxyguanine levels.

RESULTS

When the drug treatment groups were compared with the control group, the drug treatment groups' total glutathione level was higher and their malondialdehyde level was lower than that of the control group (P < 0.05), especially in the clonidine group (P < 0.0001). The 8-hydroxy-2-deoxyguanine levels of the drug treatment groups, except the lacidipine group, were significantly lower than that of the control group (P < 0.0001). There was no significant difference between the contralateral kidneys of the treatment groups and control group, according to the biochemical results. As revealed via light microscopy, clonidine and moxonidine treatment significantly reduced the tubular and glomerular damage, as well as the tubular dilation. The interstitial inflammation of the kidneys in the lacidipine group was higher than that of the other treatment groups. However, the apoptotic cell count was at a high level in both the lacidipine and metyrosine groups. The increase in the collagen content was most pronounced in the lacidipine and metyrosine groups. An examination of the contralateral kidneys showed no marked pathological findings.

CONCLUSIONS

The use of a direct or indirect α2-adrenergic receptor agonist for the temporary treatment of unilateral ureteral obstruction-induced renal damage may be important for preventing renal structural injury. A more advanced study is necessary to determine the mechanisms underlying the protective effects of these drugs with regard to renal damage in ureteral obstruction.

Investigation of the effects of the chronic administration of some antihypertensive drugs on enzymatic and non-enzymatic oxidant/antioxidant parameters in rat ovarian tissue

OBJECTIVE

In this study, effects of chronic antihypertensive drug (clonidine, methyldopa, amlodipine, ramipril, and rilmenidine) treatment on antioxidant-oxidant parameters were investigated in rat ovarian tissue.

STUDY DESIGN

Chronic drug administration for 30 days and at the end, biochemical examinations (total glutathione (tGSH), glutathione peroxidase (GPO), glutathione reductase (GR), glutathione s-transferase (GST), superoxide dismutase (SOD), nitric oxide (NO), catalase (CAT), malondialdehyde (MDA), and myeloperoxidase (MPO) analyses) were performed.

RESULTS

The levels of glutathione (GSH) and NO, and the activities of GPO, GR, GST, SOD, and CAT were measured the lowest in ramiprile group. Also in ramiprile group, the level of MDA and the activity of MPO was the highest.

CONCLUSION

We divided the drugs into four groups according to their biochemical side effect potentials in ovarian tissue: (I) Drugs which have no clear negative effect on ovarian tissue: clonidine, rilmenidine; (II) Drugs which have mild negative effect on ovarian tissue: methyldopa; (III) Drugs which have moderate negative effect on ovarian tissue: amlodipine; (IV) Drugs which have severe negative effect on ovarian tissue: ramipril. These data might be useful in the selection of the least toxic antihypertensive drug in pregnant and/or normal females.

Role of adrenal gland hormones in the anti-inflammatory effect mechanism of tamoxifen, a partial antagonist for oestrogen receptors, and relation with COX levels

OBJECTIVE

There is limited study about anti-inflammatory effect mechanism of tamoxifen. We aimed to investigate the anti-inflammatory activity of tamoxifen to see whether adrenal gland hormones have roles in the anti-inflammatory effect mechanism of tamoxifen and to evaluate the relationship between anti-inflammatory activity and cyclooxygenase (COX) level.

STUDY DESIGN

Effects of tamoxifen, indomethacin and prednisolon on carrageenan-induced inflammatory paw oedema were investigated in intact and adrenalectomised rats. Also blood adrenalin and corticosterone levels and paw tissue COX levels determined biochemically.

RESULTS

Tamoxifen (5, 10 and 20 mg/kg), indomethacin (5, 10 and 20 mg/kg) and prednisolon (5 mg/kg) produced anti-inflammatory effects in intact rats, however, they could not in adrenalectomized rats. 20 mg/kg tamoxifen produced low anti-inflammatory effect. Tamoxifen and indomethacin decreased COX-2 levels in intact rats, but not in adrenalectomised rats. Tamoxifen produced anti-inflammatory effects by decreasing adrenalin levels, as indomethacin does. 20 mg/kg tamoxifen decreased corticosterone levels.

CONCLUSIONS

Tamoxifen was seen to suppress carrageenan-induced inflammation significantly. The dose of tamoxifen that decreases adrenalin levels maximally and decreases corticosterone levels minimally was found to produce the most potent anti-inflammatory effect. The reason why indomethacin is more potent in high doses may be that it decreases adrenalin levels strongly at these doses, without decreasing corticosterone levels.

Influence of adrenal hormones in the occurrence and prevention of stress ulcers

PURPOSE

The aim of the study was to examine whether endogenous cortisol and adrenalin have a role in the formation of stress ulcers in intact and adrenalectomized rats.

METHODS

The study was composed of 4 experiments: ulcerated areas in stomachs of adrenalectomized and intact rats were measured, adrenaline (100 μg/kg) and prednisolone (5 mg/kg) were injected intraperitoneally in adrenalectomized rats, metyrapone (200 mg/kg) and metyrosine (200 mg/kg) were administered to intact rats, and metyrapone (200 mg/kg) and metyrosine (200 mg/kg) were administered orally with yohimbine (10 mg/kg) and yohimbine (10 mg/kg) alone were administered to intact rats. After 24-hour restraint stress, ulcerated areas were measured.

RESULTS

In the stomach of intact rats, the degree of stress ulcer was 7.25 times more severe than that noted in adrenalectomized rats. Furthermore, stress ulcers in adrenalectomized rats that received adrenaline or prednisolone only were fewer and less severe than rats receiving both adrenaline and prednisolone.

CONCLUSIONS

Simultaneous administration of adrenaline and prednisolone did not prevent the formation of stress ulcers. However, either of these hormones alone (adrenaline or prednisolone), in the absence of the other, repressed the formation of stress ulcers. This antiulcer activity may be related to α2-adrenergic receptor activity.

Effect of acute and chronic administration of progesterone, estrogen, FSH and LH on oxidant and antioxidant parameters in rat gastric tissue

This study was conducted to investigate whether gastro-protective and gastro-toxic effects of acute and chronic administration of progesterone, estrogen, FSH and LH were related to oxidant and antioxidant parameters. Chronic administration of progesterone at a low dose (1mg/kg), which probably could not stimulate progesterone receptors (PRs), inhibited oxidative stress of FSH in gastric tissue by suppressing FSH. Progesterone (5mg/kg) may have been caused oxidative stress as reflected by PR stimulation. FSH may have decreased antioxidant parameters and increased oxidant parameters via PRs. Chronic administration of low dose of estrogen (1mg/kg) inhibited LH and but could not stimulate alpha-2 adrenergic receptors, which resulted in oxidative stress in gastric tissue. The higher dose of estrogen (5mg/kg), however, could stimulate alpha-2 receptors, exhibited antioxidant activity in acute and chronic administration. While antioxidant activity of estrogen and LH was blocked with yohimbine (an alpha-2 adrenergic receptor blocker), mifepristone prevented the oxidative stress of progesterone and FSH in gastric tissue. It is concluded that low doses of progesterone may inhibit FSH, whereas high doses of estrogen may stimulate alpha-2 receptors, suggesting that LH could have protective and antioxidant hormone effects.