Angiotensin I converting enzyme in glycerol-induced acute renal failure in rats

Ciglitazone, a Peroxisome Proliferator-Activated Receptor γ Inducer, Ameliorates Renal Preglomerular Production and Activity of Angiotensin II and Thromboxane A2 in Glycerol-Induced Acute Renal Failure

Peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear transcription factor, modulates vascular responses to angiotensin II (AII) or thromboxane A(2) (TxA(2)) via regulation of their gene/receptor. Increased vasoconstriction and deteriorating renal function in glycerol-induced acute renal failure (ARF) may be attributed to down-regulation of PPARgamma. In this study, we investigated the effect of ciglitazone (CG), a PPARgamma inducer, on AII and TxA(2) production and activity in glycerol-induced ARF. Vascular responses to AII or 9,11-dideoxy-11alpha,9alpha-epoxymethano prostaglandin F(2alpha) (U46619), a TxA(2) mimetic, were determined in preglomerular vessels following induction of ARF with glycerol. Renal damage and function were assessed in CG-treated (9 nmol/kg for 21 days) rats. PPARgamma protein expression and activity, which were significantly lower in ARF rats, were enhanced by CG (26 and 30%). CG also increased PPARgamma mRNA by 67 +/- 6%, which was reduced in ARF. In ARF, there was significant tubular necrosis and apoptosis, a 5-fold increase in proteinuria and a 2-fold enhancement in vasoconstriction to AII and U46619. CG reduced proteinuria (49 +/- 3%), enhanced Na(+) (124 +/- 35%) and creatinine excretion (92 +/- 25%), markedly diminished tubular necrosis, and reduced ARF-induced increase in AII (40 +/- 3%) and TxA(2) (39 +/- 2%) production, the attending increase in vasoconstriction to AII (36 +/- 2%) and U46619 (50 +/- 11%), and the increase in angiotensin receptor-1 (AT(1)) (23 +/- 3%) or thromboxane prostaglandin (TP) receptor (13 +/- 1%). CG reduced free radical generation by 55 +/- 14% while elevating nitrite excretion (65 +/- 13%). Our results suggest that enhanced activity of AII and TxA(2), increased AT(1) or TP receptor expression, and renal injury in glycerol-induced ARF are consequent to down-regulation of PPARgamma gene. CG ameliorated glycerol-induced effects through maintaining PPARgamma gene.

Contribution of renal oxygenases to glycerol-induced acute renal failure in the rat

Administration of glycerol produces acute renal failure (ARF) accompanied by profound vasoconstriction. It was hypothesized that impaired arachidonic acid metabolism may contribute to the vasoconstriction through alteration of renal eicosanoids or endothelin-1 or angiotensin II stimulation of renal oxygenases. Arachidonic acid (5, 10, 25 microg) in the control kidney produced increases in perfusion pressure of 15 +/- 9, 18 +/- 8, and 43 +/- 18 mm Hg, respectively. These responses were increased 1.5-fold in glycerol-induced renal failure (p < 0.01). Indomethacin (10 microM), the cyclooxygenase inhibitor, converted arachidonic acid vasoconstriction to epoxide-mediated vasodilator responses, which were unchanged in ARF. In ARF, 5,8,11,14-eicosatetraynoic acid (10 microM), the all-purpose inhibitor of arachidonic acid metabolism; indomethacin (10 microM), a cyclooxygenase inhibitor; 5,8,11-eicosatriyenoic acid (2.5 microM), the 5- and 12-lipoxygenase inhibitor; or aminobenzotriazole (50 mM), the cytochrome P-450 monooxygenase inhibitor, markedly attenuated arachidonic acid-induced vasoconstriction by 73 +/- 11% (p < 0.01), 89 +/- 1% (p < 0.01), 62 +/- 11% (p < 0.01), and 82 +/- 2% (p < 0.01), respectively. In ARF, angiotensin II-induced vasoconstriction was amplified by 67% (p < 0.01). Eicosatetraynoic acid, eicosatriyenoic acid, and aminobenzotriazole reduced these responses by 33 +/- 6% (p < 0.05), 53 +/- 6% (p < 0.01), and 52 +/- 11% (p < 0.05), respectively. Vasoconstriction by endothelin-1 was unchanged in ARF (24 +/- 17%). However, indomethacin attenuated endothelin-1 vasoconstriction by 41 +/- 11% (p < 0.05), whereas eicosatriyenoic acid and aminobenzotriazole were without effect. These data suggest that the increased renal vascular reactivity in ARF in response to arachidonic acid involves a relatively greater production of cyclooxygenase metabolites than monoxygenase- or lipoxygenase-derived eicosanoid metabolites. Furthermore, increased angiotensin II vasoconstriction is predominantly through lipoxygenase and monoxygenase metabolic pathways, whereas for endothelin-1, increased cyclooxygenase-derived vasoconstrictor metabolites play a significant role in its amplified vasoconstrictor effect in glycerol-induced ARF.

Ascites fluid of nephrotic rats: sodium dodecyl sulphate-polyacrylamide gel electrophoresis protein pattern and the renin-angiotensin system

1. The concentration of renin and angiotensinogen (Ao) and the activity of angiotensin I-converting enzyme (ACE) was measured in the ascites fluid of nephrotic rats obtained 8 days after puromycin aminonucleoside (PAN) injection. 2. Ascites fluid, serum and urine proteins of these rats were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). 3. Renin, Ao and ACE were found in the ascites fluid and the percentage of the ratio ascites fluid/(plasma or serum) ranged from 5.9 to 9.9%. The electrophoretic analysis revealed that the ascites fluid contained low (Mr < 66 kDa) and high (Mr < 66 kDa) molecular weight proteins. Albumin and six proteins higher than 66 kDa were present both in the ascites fluid and in serum from nephrotic rats. 4. Data from the study suggest that some proteins in the ascites fluid, including renin, Ao and ACE, come from the plasma. It is possible that the loss of renin, Ao and ACE to the ascites fluid may be playing a role in the metabolic alterations of these three proteins in PAN-nephrotic rats.

Proline specific peptidases

Proline is unique among the 20 amino acids due to its cyclic structure. This specific conformation imposes many restrictions on the structural aspects of peptides and proteins and confers particular biological properties upon a wide range of physiologically important biomolecules. In order to adequately deal with such peptides, nature has developed a group of enzymes that recognise this residue specifically. These peptidases cover practically all situations where a proline residue might occur in a potential substrate. In this paper we endeavour to discuss these enzymes, particularly those responsible for peptide or protein hydrolysis at proline sites. We have detailed their discovery, biochemical attributes and substrate specificities and have provided information as to the methodology used to detect and manipulate their activities. We have also described the roles, or potential roles that these enzymes may play physiologically and the consequences of their dysfunction in varied disease states.