Dexmedetomidine and S(+)-ketamine in ischemia and reperfusion injury in the rat kidney

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Does propofol and isoflurane protect the kidney against ischemia/reperfusion injury during transient hyperglycemia?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

FUNCTIONAL AND ULTRASTRUCTURAL EVALUATION OF MYOCARDIAL PROTECTION PROVIDED BY INTERMITTENT CORONARY SINUS PERFUSION IN THE ISOLATED DOG HEART

1. The protection offered by intermittent perfusion of of cardioplegic solution through the coronary sinus was investigated in isovolumic blood-perfused dog heart preparations submitted to 60 min of ischemia and 45 min of reperfusion.2. The preparations were divided into three treatment groups: a) coronary sinus, consisting of preparations (N = 10) perfused through the coronary sinus under 40 cm water pressure; b) aortic, consisting of preparations (N = 10) perfused through the aortic stump under 100 mmHg pressure; c) control, consisting of hearts (N = 9) that were not perfused with cardioplegic solution.3. Properties of contractile capacity and relaxation were markedly impaired in the control group but were preserved to a comparable extent in the groups perfused with cardioplegic solution through the aorta and coronary sinus. Developed pressure decreased in the control group (before ischemia: 70 +/- 5.5 mmHg; after reperfusion: 35 +/- 12 mmHg; P < 0.05) and didn't vary in the aortic group (from 69 +/- 4 mmHg to 65 +/- 13 mmHg; P > 0.05) and coronary sinus group (from 69 +/- 4.6 mmHg to 60 +/- 10 mmHg; P > 0.05). Myocardial relaxation was evaluated by the +/- dp/dt ratio. In the control group there was impairment of myocardial relaxation as indicated by an increase of this index after reperfusion (from 1.05 +/- 0.05 to 1.46 +/- 0.23; P < 0.05), whereas in the aortic (from 1.10 +/- 0.13 to 1.15 +/- 0.20; P > 0.05) and the coronary sinus (from 1.03 +/- 0.14 to 1.08 +/- 0.16; P > 0.05) groups there was no variation. Ultrastructural changes in the myocardium were negligible in all three groups at the end of reperfusion.4. We conclude that intermittent perfusion of a hypothermic cardioplegic solution through the coronary sinus is effective for the protection of the myocardium during total ischemia.

Effect of uroguanylin on potassium and bicarbonate transport in rat renal tubules

The effect of uroguanylin (UGN) oil K(+) and H(+) secretion in the renal tubules of the rat kidney was studied using in vivo stationary microperfusion. For the study of K(+) secretion, a tubule was Punctured to inject a column of FDC-green-colored Ringer's solution with 0.5 mmol KCI/L 10(-6)(mol UGN/L, and oil was Used to block fluid flow. K(+) activity and transepithelial potential differences (PD) were measured with double microelectrodes (K(+) ion-selective resin vs. reference) in the distal tubules of the same nephron. During perfusion, K(+) activity rose exponentially, from 0.5 mmol/L to stationary concentration, allowing for the calculation of K(+) secretion J(K)). JK increased from 0.63 +/- 0.06 nmol.cm(-2).s(-1) in the control croup to 0.85 +/- 0.06 in the UGN group (p < 0.01). PD was -51.0 +/- 5.3 mV in the control group and -50.3 +/- 4.98 mV in the UGN group. In the presence of 10(-7) mol iberiotoxin/L, the UGN effect was abolished: JK was 0.37 +/- 0.038 nmol-cm(-2).s(-1) in the absence of, and 0.38 +/- 0.025 in the presence of, UGN. indicating its action oil rnaxi-K channels. In another series of experiments, renal tubule acidification was studied, using similar method: proximal and distal tubules were perfused with solutions containing 25 mmol NaHCO(3)/L. Acidification half-time was increased both in proximal and distal segments and, as a consequence, bicarbonate reabsorption decreased in the presence of UGN (in proximal tubules, from 2.40 +/- 0.26 to 1.56 +/- 0.21 nmol-cm(-2).s(-1)). When the Na(+)/H(+) exchanger was inhibited by 10(-4) mol hexamethylene amiloride (HMA)/L, the control and UGN groups were not significantly different. In the late distal tubule, after HMA, UGN significantly reduced J(HCO3)(-). indicating all effect of UGN oil H(+)-ATPase. These data show that UGN stimulated J(K)(+) by actin, oil maxi-K channels. and decreased J(HCO3)(-) by acting on NHE3 in proximal and H(+)-ATPase in distal tubules.

INTERACTION AMONG ZINC, GLUCOSE, AND INSULIN IN NORMAL INDIVIDUALS DURING GLUCOSE AND TOLBUTAMIDE PERFUSION

Reports in the literature have shown that acute or chronic zinc administration may cause hyperglycemia, with a fall in serum or insular insulin occurring in experimental animals. on the other hand, under conditions of both acute and chronic hyperglycemia, an increase, a decrease, or a normal level of blood zinc has been observed in studies conducted on humans. Thus, the objective of the investigation described here was to determine the relationship existing among zinc, glucose, and insulin under acute conditions. Thirty-six subjects of both sexes (mean age, 23 yr) were tested at 7:00 A.M. after a 12-h fast. Two antecubital veins of both forearms were punctured and maintained with physiological saline. Three experiments were performed in which zinc was administered orally, and hypertonic glucose and tolbutamid were administered intravenously. Blood samples were then collected over a period ranging from 93 to 240 min after the basal times of - 30 and 0 min. Hyperzincemia did not cause changes in plasma glucose or insulin either in the absence of or during perfusion of glucose. Hyperglycemia, hypoglycemia, and hyperinsulinemia did not modify serum zinc levels. These results demonstrate that acute zinc administration did not change carbohydrate metabolism and that sudden variations in glucose and insulin levels did not modify the serum profile of zinc.

Purification and biological activity of the thrombin-like substance isolated from Bothrops insularis venom

The venom of Bothrops insidaris snake, known in Brazil as jararaca ilhoa, contains a variety of proteolytic enzymes such as a thrombin-like substance that is responsible for various pharmacological effects. B. insularis venom chromatography profile showed an elution of seven main fractions. The thrombin-like activity was detected in fractions I and 111, the latter being subjected to two other chromatographic procedures, so to say DEAE and Hi Trap Benzamidine. The purity degree of this fraction was confirmed by analytical reverse phase HPLC, which displayed only one main fraction confirmed by SDS-PAGE constituting fraction III. About 5 mu g of fraction III protein potentiated the secretion of insulin induced by 2.8mM of glucose in rats isolated pancreatic beta-cells treated; the increase being around 3-fold higher than its respective control. B. insidaris lectin (BiLec; 10 mu g/mL) was also studied as to its effect on the renal function of isolated perfused rat kidneys with the use of six Wistar rats. BiLec increased perfusion pressure (PP), renal vascular resistence (RVR), urinary flow (UF) and glomerular filtration rate (GFR). Sodium (%TNa+) and chloride tubular reabsorption (%TCl-) decreased at 120 min, without alteration in potassium transport. In conclusion, the thrombin-like substance isolated from B. insularis venom induced an increase in insulin secretion, in vitro, and transiently altered vascular, glomerular and tubular parameters in the isolated rat kidney. (c) 2006 Elsevier Ltd. All rights reserved.

Effect of intraluminal distention on microvascular perfusion in the equine small colon

Objective-To determine the effect of experimental intraluminal distention on microvascular perfusion of the small colon in horses.Animals-6 mixed-breed healthy horses (mean age [+/- SD], 9.1 +/- 2 years).Procedure-Under general anesthesia, the small colon was exposed by celiotomy and 3 segments were demarcated. In 1 of these segments, intraluminal obstruction was created by placement of a latex balloon inflated to a pressure of 40 mm Hg (obstructed segment). The other segments were the sham-operated segment and the control segment. Microvascular perfusion was evaluated in the mucosal, submucosal, muscular, and serosal layers by injection of 15-mum-diameter colored microspheres into branches of the caudal mesenteric artery. Recovery of microspheres was performed by tissue digestion, washing, and centrifugation. Distribution of microspheres in the intestinal layers was evaluated by direct observation of stained frozen sections by light microscopy.Results-A significant reduction was observed in total microvascular perfusion of obstructed segments, which was 26.4% of that of control segments. This reduction was not evident in the mucosal layer.Conclusions and Clinical Relevance-Intraluminal distention of the equine small colon wall can promote ischemia by a reduction in microvascular perfusion in the intestinal wall. Intestinal layers do not seem to be affected to the same extent, because the absolute value for mucosal perfusion did not decrease in the obstructed segment.

Signaling path of the action of AVP on distal K+ secretion

Background. Previous studies from our laboratory have shown that luminal perfusion with arginine vasopressin (AVP) stimulates distal tubule secretory potassium flux (J(K)) via V1 receptors (Am J Physiol 278: F809- F816, 2000). In the present work, we investigate the cell signaling mechanism of this process.Methods. In vivo stationary microperfusion was performed in rat cortical distal tubules and luminal K was measured using double K+ resin/reference microelectrodes.Results. In control conditions, J(K) was 0.71 +/- 0.05 nmol. cm(-2).second(-1); this process was inhibited (14%) by 10(-5) mol/L 8-bromo-cyclic adenosine monophosphate (cAMP), and increased by 35% with 10(-8) mol/L phorbol ester [phorbol 12-myristate 13-acetate (PMA), which activates protein kinase C (PKC)]. During luminal perfusion with 10(-11) mol/L AVP, J(K) increased to 0.88 +/- 0.08 nmol. cm(-2).seconds(-1). In the presence of 10(-11) mol/L AVP, J(K) was not affected by 10(-4) mol/L H89, a blocker of protein kinase A (PKA), but was inhibited (45%) by 10(-5) mol/L staurosporine, an inhibitor of PKC, and by 41% during perfusion with 5 x 10(-5) mol/L of the cell Ca2+ chelator bis (2-aminophenoxy) ethane-tetraacetic acid (BAPTA). In order to study the role of Ca2+-dependent K channels in the luminal hormonal action, the tubules were perfused with 5 mmol/L tetraethylammonium chloride (TEA) or 10(-7) mol/L iberiotoxin, in the presence of AVP, and JK was significantly reduced by both agents. Iberiotoxin reduced AVP-stimulated J(K) by 36.4%, and AVP-independent J(K) (after blocking V1 receptors) by only 16%.Conclusion. The results suggest that the luminal V1-receptor effect of AVP on J(K) was mediated by the phospholipase C (PLC)/ Ca2+/PKC signaling path and not by adenylate cyclase/cAMP/PKA, therefore probably acting on maxi-potassium channels.

Renal artery clipping attenuates the progression of adriamycin nephropathy

This study was designed to analyze the impact of diminished renal perfusion pressure due to renal clipping on the rat model of adriamycin nephropathy. Male Wistar rats, divided into four groups (n = 9 per group) were injected with saline as control (C), adriamycin 3 ml/kg (Ad), saline with the left renal artery clipped (Rv), and adriamycin plus clip (AdRv). After 24 weeks mean arterial pressure (MAP), inulin, and p-aminohippurate (PAH) clearances were performed to evaluate renal function. Morphologic analysis included histologic criteria of percentage of glomerulosclerosis and tubulointerstitial lesion index (TILI). The MAP (mm Hg) was similar between Rv (143 +/- 13) and AdRv (154 +/- 20), but higher (P < .05) than C (120 +/- 8) and Ad (124 +/- 11). Inulin clearance (mL/min/100 g) in Ad (0.2 +/- 0.05) was smaller than in C (0.53 +/- 0.17) and Rv (0.4 +/- 0.01) (P < .05), and was at an intermediate level in AdRv (0.33 +/- 0.2). The level of PAH (mL/min/100 g) was normal at 1.76 in C, and diminished more in Ad (0.58) than in Rv (1.06) and AdRv (1.18) (P < .05). Both Ad and the AdRv nonclipped kidneys had the highest degree of glomerulosclerosis (33% and 25%) and TILI (7% and 8%), respectively, compared with C and Rv (both 0%), whereas the clipped kidneys displayed intermediate degrees (9% and 5%) (P < .05 v nonclipped). The data suggest that diminished perfusion pressure of the clipped kidney, by decreasing the intraglomerular pressure, protects the glomerulus from damage and attenuates the evolution of adriamycin nephropathy. Am J Hypertens 1998;11:1124-1128 (C) 1998 American Journal of Hypertension, Ltd.