In order to study the role of EDRF in diabetic hyperfiltration, the concentrations of NO2-/NO3-, the stable products of nitric oxide (NO), were measured in arterial plasma, urine, and renal venous blood in streptozotocin diabetic rats and normal control rats. In additional experiments, the renal hemodynamic and blood pressure responses to graded doses of an inhibitor of NO synthesis (Nitro-L-arginine; NLA) were measured. We found that plasma and urinary levels of NO2/NO3 are significantly higher in STZ diabetic rats (10 to 15 days) than in normal rats. Renal blood flow and GFR fell comparably in diabetic and normal rats in response to NLA infusion, although the absolute levels of RBF and GFR remained significantly higher in the diabetic rats at all doses of the inhibitor. Mean arterial blood pressure (MAP) rose in response to NLA administration, but the increase in the diabetic rats was significantly blunted as compared with the normal rats. Similarly, renal vascular resistance (RVR) increased less in the diabetic than in the normal rats at comparable doses of NLA. The blunted vasoconstrictor responses to NLA were accompanied by a smaller reduction in the levels of NO2-/NO3- in the urine of the diabetic versus the normal rats. These findings suggest that NO synthesis is increased in diabetic rats manifesting hyperfiltration and are consistent with the view that excess NO synthesis contributes to renal hyperfiltration.

A line of transgenic mice with two cointegrated transgenes, the human 1s-and a2-globin genes, linked to the 13-globin locus control region was produced and bred with mice carrying a deletion of the mouse p1iW°r-globin gene.In transgenic mice homozygous for the pOdoEr deletion (aHI3S [PMDD]; where aH is human a-globin and MD is mouse deletion), 72.5 ± 2.4% (mean ± SD) of the 1-chains are .3s and the ratio of aH_ to 1s-globin was 0.73. Introduction of a heterozygous mouse a-globin deletion into mice homozygous for the Poor deletion (aHjis[aMDI3MDDJ) resulted in 65.1 ± 8.5% %.s and a human er/P ratio of 0.89 ± 0.2. Sickling occurs in 95% of erythrocytes from aHplS [PMDD] mice after slow deoxygenation. Transmission electron microscopy revealed polymer fiber formation but not fascicles of fiber. Increased organ weight was noted in lung, spleen, and kidney of transgenic mice vs. controls that may be due to hypertrophy or increased blood volume in the lungs and/or increased tissue water content. The hemoglobin content of lung, spleen, and kidney was also elevated in transgenic animals due to trapped hemoglobin and/or increased blood volume. When transgenic and control mice were examined by magnetic resonance imaging at 9.4 tesla, some transgenic animals had enlarged kidneys with prolonged relaxation time, consistent with increased organ weight and water content. The glomerular filtration rate was elevated in transgenic animals, which is characteristic of young sickle cell patients. Furthermore, exposure to hypoxia resulted in signifcantly decreased hematocrit, increased erythrocyte density, and induced a urineconcentrating defect. We conclude that the transgenic mouse line reported here has chronic organ damage and further hematological and organ dysfunction can be induced by hypoxia.The development of several different transgenic mouse models for sickle cell disease (1-7) has the potential ofelucidating the mechanism of vasoocclusion in sickle cell anemia. Sickle cell vasoocclusion is a multifactorial event that involves obstruction of the microcirculation by irreversibly sickled cells (8), nondeformable polymer-filled deoxygenated cells, and adhesion by deformable discocytes capable of contributing to the initiation or aggravation of vasoocclusion (9-11). The time interval or delay time between deoxygenation and the onset ofpolymer formation may play a role in determining both the frequency and severity of vasoocclusion (12).Several organs are particularly susceptible to obstruction and ensuing damage in sickle cell disease. In this paper we will focus on the spleen, the kidneys, and the lungs. In the mouse, the spleen is both the site of erythrocyte (RBC) production and destruction. In sickle cell patients, the spleen is the site of infarction (13), potential sequestration (14), and autospenectomy in the second decade of life. The detailed pathophysiology of vasoocclusion need not be the same in each organ. For example, in some organs, such as the lung and kidney, the response to hypoxia is vasoconstriction...

A B S T R A C T In order to investigate the syndrome of postobstructive diuresis, clearance and micropuncture studies were carried out in rats after relief of 24 hr of bilateral (BUL) or unilateral (UUL) ureteral ligation. In rats with BUL, a striking diuresis and natriuresis occurred when the obstruction to one kidney (the experimental kidney) was relieved. The results were not influenced by administration of vasopressin or d-aldosterone. Whole kidney clearances of inulin and p-aminohippuric acid (PAH) in the experimental kidney were reduced to 10% and 20% of normal, respectively. Superficial nephron inulin and PAH clearances were also reduced, but only to 40% and 45%, respectively. These findings suggest a heterogeneity of nephron function in which deep nephrons were functioning poorly or not at all. To investigate the site of impaired tubular reabsorption in the surface nephrons, absolute and fractional water reabsorption was measured. Absolute reabsorption was found to be decreased all along the nephron. Fractional reabsorption in proximal tubules was normal, as indicated *by an average endproximal tubular fluid per plasma inulin (TF/Pi.) of 2.16 vs. 2.30 in controls. TF/Pri was markedly decreased in distal tubules (2.91 vs. 8.02) and final urine (5.56 vs. 263). These observations indicate that the major sites of impaired sodium reabsorption leading to the diuresis were beyond the proximal tubule.

The alpha H beta S [beta MDD] mouse is a useful model for studying renal functional abnormalities in sickle cell disease. We previously reported that these mice develop a urine concentrating defect when chronically exposed to a low oxygen environment. In the present study, we measured glomerular filtration rate (GFR), urinary excretion of NO2 s+ NO3, the stable products of nitric oxide (NO), and the abundance of endothelial constitutive nitric oxide synthase (NOS III) and inducible nitric oxide synthase (NOS II) in the kidneys by Western blot. Immunohistochemistry was also carried out. We found that GFR is significantly higher in the transgenic mice than in controls. The urinary NO2 + NO3/creatinine ratio was also higher. The Western blots revealed that both NOS III and NOS II are markedly increased in the kidneys of transgenic mice as compared to normal control mice. Immunohistochemistry localized NOS III reactivity in proximal convoluted cells in the cortex of control and alpha H beta S [beta MDD] mice. NOS II immunostaining was not seen in control mice but was clearly evident in glomeruli and distal nephron segments of the alpha H beta S [beta MDD] mice. These observations suggest that NOS II is induced in glomeruli and distal nephrons of the alpha H beta S [beta MDD] mice. An increase in synthesis of NO may occur in the glomeruli as a result of NOS II induction, and this may contribute to the hyperfiltration in these mice.