beta-Adrenoceptor stimulation provokes cardiac oxidative stress. In the acute phase of ISO infusion, ROS are important activators of cardiac MAP kinase cascades; while, in the chronic phase, ROS may participate in cardiac remodeling, especially in respect to wall stiffness, based on fibrogenesis.

Steroidogenic acute regulatory protein (StAR) is a 30-kDa protein involved in the transport of cholesterol to the inner mitochondrial membrane and thus plays a key role in steroid biosynthesis. To clarify the implications of this protein in neurosteroid biosynthesis, we examined the possible expression of a StAR transcript in the adult rat CNS and detected it. cDNA cloning and sequencing analysis revealed that two forms of StAR mRNAs are expressed in the brain in the same manner as in the adrenal gland, indicating that they are fully functional and not minor gene transcripts. An RNase protection assay quantitatively revealed that the amount of the rat StAR transcript in brain was two to three orders of magnitude lower than that in the adrenal gland. An in situ hybridization study, involving antisense riboprobes, revealed that StAR transcripts were abundant in the cerebral cortex, hippocampus, dentate gyrus, olfactory bulb, cerebellar granular layer, and Purkinje cells. Furthermore, other steroidogenic enzymes, side-chain cleavage cytochrome P-45O~~(CYP XIA1) and 3/3-hydroxysteroid dehydrogenase/z~isomerase (EC 1.1.1 .145), were found tobe coexpressed in the hippocampus, dentate gyrus, cerebellar granular layer, and Purkinje cells. These findings strongly indicate that neurosteroids are synthesized in a region-specific manner in the brain. Key Words: Steroidogenic acute regulatory protein -Brain-Neurosteroid-In situ hybridization -Ribonuclease protection assay-Cholesterol side-chain cleavage enzyme.

Whether temporary angiotensin II (AngII) blockade at the prediabetic stage attenuates renal injury in type 2 diabetic OLETF rats later in life was investigated. OLETF rats were treated with an AT 1 receptor antagonist (olmesartan, 0.01% in food), angiotensin-converting enzyme inhibitor (temocapril, 0.01% in food), a combination of the two, or hydralazine (25 mg/kg per d) at the prediabetic stage (4 to 11 wk of age) and then monitored without further treatment until 50 wk of age. At 11 wk of age, blood glucose levels and urinary protein excretion (U protein V) were similar between OLETF and control LETO rats. However, OLETF rats showed higher kidney AngII contents and type IV collagen mRNA expression than LETO rats at this age. These decreased with olmesartan, temocapril, and a combination of these but not with hydralazine. At 50 wk of age, diabetic OLETF rats showed higher BP, U protein V, and intrarenal AngII levels than LETO rats. Temporary AngII blockade did not affect glucose metabolism or the development of hypertension in OLETF rats but significantly suppressed proteinuria and ameliorated glomerular injury. However, no parameters were affected by temporary hydralazine treatment. The present study demonstrated that intrarenal AngII and type IV collagen expression are already augmented long before diabetes becomes apparent in OLETF rats. Furthermore, temporary AngII blockade at the prediabetic stage attenuates the progression of renal injury in these animals. These data suggest that early AngII blockade could be an effective strategy for preventing the development of type 2 diabetic renal injury later in life. D iabetic nephropathy is a major complication in diabetes and a leading cause of end-stage renal failure, which causes disabilities and a high mortality rate in patients with this disease (1). The mechanisms underlying the development of diabetic nephropathy are extremely complex; however, the potential role of the renin-angiotensin system (RAS) has been suggested (2-13). Recent studies indicate that in diabetes, intrarenal generation of angiotensin II (AngII) is elevated despite suppressed circulating RAS (5,6). Furthermore, AT 1 receptor blockers (ARB) or angiotensin-converting enzyme inhibitors (ACEI) have been shown to attenuate the progression of diabetic nephropathy (3,4,7-13). Several clinical trials have shown that ARB are more effective than traditional antihypertensive therapies in reducing renal failure progression in patients with type 2 diabetes and that the renoprotective effects of ARB are independent of their antihypertensive actions (8 -11). Of interest, it has also been shown that ACEI treatment of normotensive patients with diabetes and little or no proteinuria (early stages of diabetic nephropathy) results in long-term stabilization of plasma creatinine levels and urinary protein excretion rates (U protein V) (12,13). These observations suggest that angiotensin blockade has clinical benefits for patients who have diabetes and have no or early signals of renal disease.It has been sho...

Abstract-The present study was performed to examine the hypothesis that autoregulation-related changes in renal vascular resistance (RVR) are mediated by extracellular ATP. By use of a microdialysis method, renal interstitial concentrations of ATP and adenosine were measured at different renal arterial pressures (RAPs) within the autoregulatory range in anesthetized dogs (nϭ12). RAP was reduced in steps from the ambient pressure (131Ϯ4 mm Hg) to 105Ϯ3 mm Hg (step 1) and 80Ϯ2 mm Hg (step 2). Renal blood flow and glomerular filtration rate exhibited efficient autoregulation in response to these changes in RAP. RVR decreased by 22Ϯ2% in step 1 (PϽ0.01) and 38Ϯ3% in step 2 (PϽ0.01).The control renal interstitial concentration of ATP was 6.51Ϯ0.71 nmol/L and decreased to 4.51Ϯ0.55 nmol/L in step 1 (PϽ0.01) and 2.77Ϯ0.47 nmol/L in step 2 (PϽ0.01). In contrast, the adenosine concentrations (117Ϯ6 nmol/L) were not altered significantly. Changes in ATP levels were highly correlated with changes in RVR (rϭ0.88, PϽ0.0001).Further studies demonstrated that stimulation of the tubuloglomerular feedback (TGF) mechanism by increasing distal volume delivery elicited with acetazolamide also led to increases in renal interstitial ATP concentrations, whereas furosemide, which is known to block TGF responses, reduced renal interstitial fluid ATP concentrations. The data demonstrate a positive relation between renal interstitial fluid ATP concentrations and both autoregulation-and TGF-dependent changes in RVR and thus support the hypothesis that changes in extracellular ATP contribute to the RVR adjustments responsible for the mechanism of renal autoregulation. (Circ Res. 2000;86:656-662.)Key Words: ATP Ⅲ renal autoregulation Ⅲ tubuloglomerular feedback Ⅲ renal interstitium Ⅲ adenosine T he purine nucleotide ATP, an intracellular energy source, is gaining recognition for its paracrine role in regulating skeletal and heart muscle contractility 1,2 as well as vascular tone in several tissues. 1-5 ATP has been shown to be released from endothelial cells, 6 epithelial cells, 7 smooth muscle cells, 6,8 myocardium, 9 and perivascular nerves. 10 Extracellular ATP exerts a substantial influence on hemodynamic function, acting via P2 purinoceptors, on a variety of tissues and organs, 2-5 including the kidney. 4,5,[11][12][13][14][15] A growing body of evidence obtained in both dogs and rats supports the hypothesis that extracellular ATP exerts a role in mediating renal autoregulatory vascular resistance responses, 14 -18 which are caused by active adjustments of vascular smooth muscle tone, primarily in the afferent arterioles. 14,15 Studies using the isolated blood-perfused juxtamedullary nephron preparation demonstrated that ATP, superfused over the renal microvessels, exerts selective afferent arteriolar vasoconstriction without affecting efferent arteriolar tone, 19,20 which is an important criterion for the agent mediating autoregulatory behavior. 14,15 This occurrence is due to the selective localization of P2 purinoceptors, which have...

Abstract-Recently, we demonstrated that in rats treated chronically with aldosterone and salt, severe tubulointerstitial fibrosis is associated with the activation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases (ERK1/2). Here, we investigated whether aldosterone stimulates collagen synthesis via ERK1/2-dependent pathways in cultured rat renal fibroblasts. Gene expression of mineralocorticoid receptor (MR) and types I, II, III, and IV collagen was measured by real-time polymerase chain reaction (PCR). MR protein expression and ERK1/2 activity were evaluated by Western blotting analysis with anti-MR and anti-phospho-ERK1/2 antibodies, respectively. Collagen synthesis was determined by [ 3 H]-proline incorporation. Significant levels of MR mRNA and protein expression were observed in rat renal fibroblasts. Treatment with aldosterone (0.1 to 10 nmol/L) increased ERK1/2 phosphorylation in a concentration-dependent manner with a peak at 5 minutes. Aldosterone (10 nmol/L) also increased the mRNA levels of types I, III, and IV collagen at 36 hours but had no effect on the type II collagen mRNA level.[3 H]-proline incorporation was significantly increased by aldosterone in both the medium and cell layer at 48 hours. Aldosterone-induced ERK1/2 phosphorylation was markedly attenuated by pretreatment with eplerenone (10 mol/L), a selective MR antagonist, or PD98059 (10 mol/L), a specific inhibitor of MAPK kinase/ERK kinase, which is the upstream activator of ERK1/2. In addition, both eplerenone and PD98059 prevented the aldosterone-induced increases in types I, III, and IV collagen mRNA and [ Key Words: aldosterone Ⅲ collagen Ⅲ fibroblasts Ⅲ mineralocorticoids R ecent studies have indicated the usefulness of mineralocorticoid receptor (MR) antagonists in ameliorating renal injury. [1][2][3][4][5][6][7][8][9][10][11][12][13] In stroke-prone spontaneously hypertensive rats 4 and rats treated with angiotensin II and a nitric oxide synthase inhibitor, 5 cyclosporine A, 6 or radiation, 7 MR antagonists had no effect on systemic blood pressure but markedly ameliorated glomerular and tubulointerstitial fibrosis. In clinical studies, the addition of a nonselective MR antagonist, spironolactone, to angiotensin-converting enzyme inhibitors had no hemodynamic effects but markedly reduced proteinuria in patients with chronic renal failure 8 and early diabetic nephropathy. 9 It has also been shown that monotherapy with spironolactone 10 or eplerenone, 11 a selective MR antagonist, is more effective than angiotensin-converting enzyme inhibitors in reducing proteinuria in hypertensive patients. Furthermore, White et al 12 showed that in hypertensive patients, eplerenone had a similar blood pressurelowering effect to that of a calcium antagonist, amlodipine, but reduced the urinary albumin-to-creatinine ratio to a greater extent. These observations suggest that MR blockade has renoprotective effects through mechanisms that cannot be simply explained by blood pressure and hemodynamic changes.R...