Quantitative assessment of proliferative effects of oral vanadium on pancreatic islet volumes and beta cell numbers of diabetic rats

Background: Oral vanadyl sulfate [vanadium] induces normoglycemia, proliferates beta cells and prevents pancreatic islet atrophy in streptozotocin-induced diabetic rats. Soteriological method is used to quantitate the proliferative effects of vanadium on beta-cell numbers and islet volumes of normal and diabetic rats. Adult male Sprague-Dawley rats were made diabetic with intravenous streptozotocin injection [40 mg/kg]. Normal and diabetic rats were divided into four groups. While control normal and diabetic [CD] groups used water, vanadium-treated normal [VTN] and diabetic [VTD] groups used solu ons containing vanadyl sulfate [0.51 mg/mL, VOSO[4]+5H[2]O]. Tail blood samples were used to measure blood glucose [BG] and plasma insulin. Two months after treatment, rats were sacrificed, pancreata prepared, and stereology method was used to quantitatively evaluate total beta cell numbers [TBCN] and total islet volumes [TISVOL]

Results: Normoglycemia persisted in VTN with significantly decreased plasma insulin [0.19 +/- 0.08 vs. 0.97+/-0.27 ng/dL, P<0.002]. The respec ve high BG [532h49 vs. 144+/-46 mg/dL, P<0.0001] and reduced plasma insulin [0.26 +/- 0.15 vs. 0.54+0.19 ng/dL, P<0.002] seen in CD were reversed in VTD during vanadium treatment or withdrawal. While the induction of diabetes, compared to their control, significantly decreased TISVOL [1.9 +/- 0.2 vs. 3.03 +/- 0.6 mm[3], P<0.003] and TBCN [0.99 +/- 0.1 vs. 3.2 +/- 0.2 x 10[6], P<0.003], vanadium treatment significantly increased TISVOL [2.9 +/- 0.8 and 4.07 +/- 1.0 mm[3], P<0.003] and TBCN [1.5 +/- 0.3 and 3.8 +/- 0.6 x 10[5], P<0.03

Conclusion: Two-month oral vanadium therapy in STZ-diabetic rats ameliorated hyperglycemia by partially restoring plasma insulin. This action was through proliferative actions of vanadium in preventing islet atrophy by increasing beta-cell numbers

Does the relief of glucose toxicity act as a mediator in proliferative actions of vanadium on pancreatic islet beta cells in streptozocin diabetic rats?

Data shows vanadium protects pancreatic beta cells [BC] from diabetic animals. Whether this effect is direct or through the relief of glucose toxicity is not clear. This study evaluated the potential effect of oral vanadyl sulfate [vanadium] on glycemic status and pancreatic BC of normal and diabetic rats. Rats were divided into five groups of normal and diabetic. Diabetes was induced with streptozocin [40 mg/kg, i.v.]. Normal rats used water [CN] or vanadium [1 mg/ml VOSO4, VTN]. Diabetic rats used water [CD], water plus daily neutral protamine Hagedorn insulin injection [80 U/kg, ITD] or vanadium [VTD]. Blood samples were taken for blood glucose [BG, mg/dL] and insulin [ng/dL] measurements. After two months, the pancreata of sacrificed rats were prepared for islet staining. Pre-treated normal BG was 88 +/- 2, and diabetic BG was 395 +/- 9. The final BG in CD, VTD, and ITD was 509 +/- 22, 138 +/- 14, and 141 +/- 14, respectively. Insulin in VTN [0.75 +/- 0.01] and VTD [0.78 +/- 0.01] was similar, higher than CD [0.51 +/- 0.07] but lower than CN [2.51 +/- 0.02]. VTN islets compared to CN had larger size and denser central core insulin immunoreactivity with plentiful BC. CD and ITD islets were atrophied and had scattered insulin immunoreactivity spots and low BC mass. VTD islets were almost similar to CN. Besides insulin-like activity, vanadium protected pancreatic islet BC, and the relief of glucose toxicity happening with vanadium had a little role in this action

Candesartan attenuates ischemic brain edema and protects the blood-brain barrier integrity from ischemia/reperfusion injury in rats

Angiotensin II [Ang II] has an important role on cerebral microcirculation; however, its direct roles in terms of ischemic brain edema need to be clarified. This study evaluated the role of central Ang II by using candesartan, as an ATI receptor blocker, in the brain edema formation and blood-brain barrier [BBB] disruption caused by ischemia/reperfusion [I/R] injuries in rat. Rats were exposed to 60-min middle cerebral artery [MCA] occlusion. Vehicle and non-hypotensive doses of candesartan [0.1 mg/kg] were administered one hour before ischemia. Neurological dysfunction scoring was evaluated following 24 h of reperfusion. Animals were then decapitated under deep anesthesia for the assessments of cerebral infarct size, edema formation, and BBB permeability. The outcomes of 24 h reperfusion after 60-min MCA occlusion were severe neurological disability, massive BBB disruption [Evans blue extravasation = 12.5 +/- 1.94 microg/g tissue], 4.02% edema, and cerebral infarction [317 + 21 mm[3]]. Candesartan at a dose of 0.1 mg/kg, without changing arterial blood pressure, improved neurological dysfunction scoring together with significant reductions in BBB disruption [54.9%], edema [59.2%], and cerebral infarction [54.9%]. Inactivation of central ATI receptors, if not accompanied with arterial hypotension, protected cerebral micro-vasculatures from damaging effects of acute stroke

Blockade of central angiotensin ii at, receptor protects the brain from ischemia/reperfusion injury in normotensive rats

Stroke is the third leading cause of invalidism and death in industrialized countries. There are conflicting reports about the effects of Angiotensin II on ischemia-reperfusion brain injuries and most data have come from chronic hypertensive rats. In this study, hypotensive and non-hypotensive doses of candesartan were used to investigate the effects of angiotensin II ATj receptor blockade by transient focal cerebral ischemia in normotensive rats. In this experimental study, 48 male Sprague-Dawley rats were randomly divided into four groups [n=12]. Sham group, the control ischemic group, and two ischemic groups received candesartan at doses of 0.1 or 0.5 mg/kg at one hour before ischemia. Transient focal cerebral ischemia was induced by 60 minutes occlusion of the middle cerebral artery, followed by 24 h reperfusion. The neurological deficit score was evaluated at the end of the reperfusion period. The total cortical and striatal infarct volumes were determined using triphenyltetrazolium chloride staining technique. Tissue swelling was calculated for the investigation of ischemic brain edema formation. In comparison with the control ischemic group, AT[1], receptor blockade with both dose of candesartan [0.1 or 0.5 mg/ kg] significantly improved neurological deficit and lowered cortical and striatal infarct sizes. In addition, pretreatment with candesartan significantly reduced ischemia induced tissue swelling. Angiotensin II by stimulating AT1 receptors, participates in ischemia-reperfusion injuries and edema formation. AT[1] receptor blockade with candesartan decreased ischemic brain injury and edema and improved neurological outcome

Attenuation of focal cerebral ischemic injury following post- ischemic inhibition of angiotensin converting enzyme [ACE] activity in normotensive rat

Central renin angiotensin system has an important role on the cerebral microcirculation and metabolism. Our previous work showed that inhibition of angiotensin converting enzyme [ACE] activity prior to induction of ischemia protected the brain from severe ischemia/reperfusion [I/R] injuries. This study evaluated the impacts of post-ischemic inhibition of ACE, enalapril, on brain infarction in normotensive rats. Rats were anesthetized with chloral hydrate [400 mg/kg]. Focal cerebral ischemia was induced by 60-min intraluminal occlusion of right middle cerebral artery [MCA]. Intraperitoneal injection of enalapril [0.03 or 0.1 mg/kg] was done after MCA reopening [reperfusion]. Neurological deficit score [NDS] was evaluated after 24 h and the animals randomly assigned for the assessments of infarction, absolute brain water content [ABWC] and index of brain edema. Severe impaired motor functions [NDS = 2.78 +/- 0.28], massive infarction [cortex = 214 +/- 19 mm[3], striatum = 86 +/- 5 mm[3]] and edema [ABWC = 83.1 +/- 0.46%] were observed in non-treated ischemic rats. Nonhypotensive dose of enalapril [0.03 mg/kg] significantly reduced NDS [1.5 +/- 0.22], infarction [cortex = 102 +/- 16 mm[3], striatum = 38 +/- 5 mm[3]] and edema [ABWC = 80.9 +/- 0.81%]. Enalapril at dose of 0.1 mg/kg significantly lowered arterial pressure could not improve NDS [2.0 +/- 0.45] and reduce infarction [cortex = 166 +/- 26 mm[3], striatum = 71 +/- 11 mm[3]]. Post-ischemic ACE inhibition in the normotensive rats without affecting arterial pressure protects the brain from reperfusion injuries; however, this beneficial action is masked by hypotension

Contribution of Nitric Oxide Synthase [NOS] Activity in Blood-Brain Barrier Disruption and Edema after Acute Ischemia/ Reperfusion in Aortic Coarctation-Induced Hypertensive Rats

Nitric oxide synthase [NOS] activity is increased during hypertension and cerebral ischemia. NOS inactivation reduces stroke-induced cerebral injuries, but little is known about its role in blood-brain barrier [BBB] disruption and cerebral edema formation during stroke in acute hypertension. Here, we investigated the role of NOS inhibition in progression of edema formation and BBB disruptions provoked by ischemia/reperfusion injuries in acute hypertensive rats. Rats were made acutely hypertensive by aortic coarctation. After 7 days, the rats were randomly selected for the recording of carotid artery pressure, or regional cerebral blood flow [rCBF] using laser Doppler. Ishcemia induced by 60-min middle cerebral artery occlusion [MCAO], followed by 12-h reperfusion. A single i.p. dose of L-NAME [1 mg/kg] was injected before MCAO. After evaluation of neurological disabilities, rats were slaughtered under deep anesthesia to assess cerebral infarction volume, edema, or BBB disruption. A 75-85% reduction in rCBF was occurred during MCAO which returned to pre-occluded levels during reperfusion. Profound neurological disabilities were evidenced after MCAO alongside with severe cerebral infarctions [628 +/- 98 mm[3]], considerable edema [4.05 +/- 0.52%] and extensive BBB disruptions [Evans blue extravasation, 8.46 +/- 2.03 [microg/g]. L-NAME drastically improved neurological disabilities, diminished cerebral infarction [264 +/- 46 mm[3]], reduced edema [1.49 +/- 0.47%] and BBB disruption [2.93 +/- 0.66 microg/g]. The harmful actions of NOS activity on cerebral microvascular integrity are intensified by ischemia/reperfusion injuries during acute hypertension. NOS inactivation by L-NAME preserved this integrity and diminished cerebral edema

Local administration of L-Arginine accelerates wound closure

The process of wound healing involves tightly integrated events including inflammation, granulation tissue formation and remodeling. Systemic administration of L-arginine promotes wound healing but its global side effects are undesirable. To confine the action of L-arginine at the site of injury, we tested the effects of local administration of L-arginine on the healing of excisional wound in the rat. Full thickness excisional wounds were generated on the dorsum of adult male rats. The test wounds received 200 micro m or 400 micro m of L-arginine on day 3 and 5 post-wounding. Normal saline was injected into the sham wounds which were otherwise treated as the test wounds. Control wounds remained unmanipulated. The wound size was monitored daily by imaging. To determine the rate of wound closure, wound images were scanned and the rate of size reduction was analyzed and quantified by ScnImage software. The repaired tissues were harvested on day 12 post-wounding. The tissue sections were prepared and stained for microscopic examination. Wounds treated with L-arginine showed a significant increase in the rate of wound closure. The morphology of basal keratinocytes was altered, and the thickness of neoepidermis was markedly reduced in the wounds treated with L-arginine. Both tested dose of L-arginine were equally effective. Local administration of L-arginine accelerates wound closure and has profound effects on keratinocytes performance during the process of healing. Therefore, it can be potentially used for treatment of skin disorders, in particular, those characterized by hyperkeratosis

Effect of angiotensin II on blood flow in acute and chronically inflamed knee joints of rabbits: the role of nitric oxide

Angiotensin converting enzyme [ACE] upregulation in stromal cells of joints affected by rheumatoid arthritis may lead to higher tissue angiotensin II that is a vasoconstrictor and mitogen factor. To date, the role of angiotensin II on regulating blood flow in inflamed joints has not been studied. Acute and chronic joint inflammation was induced in rabbits by intra-articular injection of carrageenan and antigen-induced arthritis method, respectively. The ACE level of synovial fluid and the response of joint blood flow to angiotensin II, angiotensin II receptor antagonist, and the role of nitric oxide [NO] in modulation of the effects of angiotensin II on joint blood vessels were examined The synovial fluid level of ACE was significantly increased during the process of inflammation and angiotensin II increased joint vascular resistance dose-dependently in both acute and chronically inflamed joints. The angiotensin 1 receptor antagonist losartan completely blocked the vasoconstrictor effect of angiotensin II on joint blood vessels and induced vasodilatation. Nitric oxide synthase inhibitor N-omega -nitro L- arginine methyl ester [L-NAME] increased joint vascular resistance and augmented vascular response of inflamed joints to angiotensin II. Angiotensin II receptors in joint blood vessels are angiotensin -1 subtype, and inflammation significantly increases the activity of synovial fluid ACE. Nitric oxide plays a significant role on regulating joint blood flow and in modulation of angiotensin 1 receptor-mediated vasoconstriction of inflamed joint blood vessels

Aminoguanidine reduces infarct volume and improves neurological dysfunction in transient model of focal cerebral ischemia in rat

Focal cerebral ischemia [Stroke] is the cessation or severe reduction of blood flow to an area of the brain that through activation of a complex cytotoxic cascade results in neuronal cell death. The present study was designed to examine the effects of post-ischemic treatment with aminoguanidine [AG] on cortical, striatal infarct volume as well as neurological dysfunctions. Rats [n=23] were allocated to sham, saline or AG [300 mg/kg]-treated groups. Ischemia was induced by 90 minutes middle cerebral artery occlusion, followed by 24 hrs reperfusion. Saline or AG was administered intraperitoneal at one hour after induction of ischemia. At the end of 24hrs reperfusion, neurological deficit score was tested and cortical, striatal infarct volumes were determined by Triphenyltetrazolium chloride staining. Administration of AG [300 mg/kg] at one hours after ischemia resulted in a significantly lower cortical [85 +/- 25 vs. 210 +/- 13 mm[3]], striatal [35 +/- 5 vs. 58 +/- 10 mm[3]] infarct volumes, and neurological deficit score [1.88 +/- 0.23vs.2.67 +/- 0.21]. Our findings indicate that aminoguanidine is a potent neuroprotective in rat model of transient focal cerebral ischemia. The future studies are required to clear cerebroprotective mechanism of aminoguanidine and possible use of this agent as a therapeutic target in stroke patients