Nearly all renal tubular epithelial cells express insulin receptor. The insulin receptor in the distal tubule appears to modulate BP, but the role of the insulin receptor in the proximal tubule is unknown. Here, we selectively knocked out the insulin receptor from the proximal tubules of mice. Western blotting confirmed a two-to three-fold reduction in renal cortical homogenate insulin receptor-b among knockout mice compared with wild-type littermates. Young knockout mice exhibited a mildly diabetic phenotype, evidenced by higher fasting plasma glucose levels than wild-type mice. Assessments by hyperinsulinemic-euglycemic clamp and a glucose tolerance test revealed no differences in insulin sensitivity or overt pancreatic function, respectively. Renal cortical mRNA expression and enzyme activity of glucose-6-phosphatase, which catalyzes the final step of glucose production, were significantly higher in knockout mice. Taken together, these results support a role for insulin receptor in the proximal tubule in the modulation of systemic glucose levels. Downregulation of the insulin receptor in the proximal tubule, which occurs in insulinresistant states, may promote hyperglycemia through enhanced gluconeogenesis.

To elucidate the role of the insulin receptor (IR) in collecting duct (CD), we bred mice with IR selectively deleted from CD principal cells using an aquaporin-2 promoter to drive Cre-recombinase expression. Young, adult male knockout (KO) mice had altered plasma and electrolyte homeostasis under high- (HS) and low-sodium (LS) diets, relative to wild-type (WT) littermates. One week of LS feeding led to a significant reduction in urine potassium (K(+)) and sodium (Na(+)) excretion in KO, and a reduction in the ratio of Na(+) to chloride (Cl(-)) in plasma, relative to WT. HS diet (1 wk) increased plasma K(+) and reduced urine Na(+) to Cl(-) ratio in the KO. Furthermore, KO mice had a significantly (P = 0.025) blunted natriuretic response to benzamil, an epithelial sodium channel (ENaC) antagonist. Western blotting of cortex homogenates revealed modestly, but significantly (∼15%), lower band density for the β-subunit of ENaC in the KO vs. WT mice, with no differences for the α- or γ-subunits. Moreover, blood pressure (BP), measured by radiotelemetry, was significantly lower in KO vs. WT mice under basal conditions (mmHg): 112 ± 5 (WT), 104 ± 2 (KO), P = 0.023. Chronic insulin infusion reduced heart rate in the WT, but not in the KO, and modestly reduced BP in the WT only. Overall, these results support a fundamental role for insulin through its classic receptor in the modulation of electrolyte homeostasis and BP.

The phosphorylated form of histone H2A.X (γ-H2AX) is a well-documented early, sensitive and selective marker of DNA double-strand breaks (DSBs). Previously we found that excessive glutamatergic activity increased γ-H2AX in neurons in vitro. Here we evaluated γ-H2AX formation in the adult rat brain following neuronal excitation evoked by seizure activity in vivo. We found that brief, repeated electroconvulsive shock (ECS)-induced seizures (three individual seizures within 60 min) did not trigger an increase γ-H2AX immunostaining. In contrast, a cluster of 5–7 individual seizures evoked by kainic acid (KA) rapidly (within 30 min) induced γ-H2AX in multiple neuronal populations in hippocampus and entorhinal cortex. This duration of seizure activity is well below threshold for induction of neuronal cell death, indicating that the γ-H2AX increase occurs in response to sublethal insults. Moreover, an increase in γ-H2AX was seen in dentate granule cells which are resistant to cell death caused by KA-evoked seizures. With as little as a 5 min duration of status epilepticus (SE), γ-H2AX increased in CA1, CA3 and entorhinal cortex, to a greater extent than observed after the clusters of individual seizures, with still greater increases after 120 min of SE. Our findings provide the first direct demonstration that DNA DSB damage occurs in vivo in the brain following seizures. Furthermore, we found that the γ-H2AX increase caused by 120 min of SE was prevented by neuroprotective preconditioning with ECS-evoked seizures. This demonstrates that DNA DSB damage is an especially sensitive indicator of neuronal endangerment, and that it is responsive to neuroprotective intervention.

To elucidate the role of the insulin receptor (IR) on kidney nitric oxide generation and blood pressure (BP) control, we generated mice with targeted deletion of renal tubule IR using loxP recombination driven by a Ksp-cadherin promoter. Male knockout (KO) and wild-type (WT) littermates (~4 mo old) were transitioned through three 1-wk treatments: 1) low-NaCl diet (0.085%); 2) high-NaCl diet (HS; 5%); and 3) HS diet plus 3 mM tempol, a superoxide dismutase mimetic, in the drinking water. Mice were then switched to medium-NaCl (0.5%) diet for 5 days and kidneys harvested under pentobarbital anesthesia. Twenty-four-hour urinary nitrates plus nitrites were significantly higher in the WT mice under HS (2,067 ± 280 vs. 1,550 ± 230 nmol/day in WT and KO, respectively, P < 0.05). Tempol attenuated genotype differences in urinary nitrates plus nitrites. A rise in BP with HS was observed only in KO mice and not affected by tempol (mean arterial pressure, dark period, HS, 106 ± 5 vs. 119 ± 4 mmHg, for WT and KO, respectively, P < 0.05). Renal outer medullary protein levels of nitric oxide synthase (NOS) isoforms by Western blot (NOS1-3 and phosphorylated-S1177-NOS3) revealed significantly lower band density for NOS1 (130-kDa isoform) in the KO mice. A second study, when mice were euthanized under HS conditions, confirmed significantly lower NOS1 (130 kDa) in the KO, with an even more substantial (>50%) reduction of the 160-kDa NOS1 isoform. These studies suggest that the loss of renal IR signaling impairs renal nitric oxide production. This may be important in BP control, especially in insulin-resistant states, such as the metabolic syndrome.

The polymorphism of pulmonary tuberculosis, the exceptional versatility of its clinical manifestations, unexpected turns in the course, various combinations with lesions of other organs - all this against the background of the social significance of the problem of tuberculosis creates a number of difficulties for the doctor not only in recognizing the disease, but also in choosing the paths along which it should unfold medical and social therapy.

The ability to “escape” by natriuresis from aldosterone infusion coupled to high‐NaCl (HS) diet may be influenced by sex steroids, but also more subtly by the sex chromosomal complement (SCC), i.e., XX or XY. We used a novel transgenic line of mice (four‐core genotypes, FCG) in which gonadal sex (male, M; or female, F) segregates independently from the SCC. FCG mice were bred in house: 1) XX‐F, 2) XY‐F, 3) XX‐M, and 4) XY‐M, and were gonadectomized at 2 months to remove masking effects of sex steroids. Mice (8/genotype) were started on a low‐NaCl (0.085%) diet then implanted with aldosterone‐infusing osmotic minipumps (40 μg/40 g·bw/d). After 3‐days, mice were switched to a HS (5% NaCl) diet. XX mice had significantly higher urine volume, urine sodium, and urine potassium excretion in the HS period, as compared XY. This effect was especially prominent in the XX‐F where sodium excretion on the 3rd day of HS was over 100% higher than in the XY‐M. No differences in food intake were found, although M mice were significantly heavier (about 20–30%). Aldosterone infusion alone caused a modest rise in BP (measured by radiotelemetry) in the XX (5–10 mm Hg), but not the XY. HS plus aldosterone led to a further rise in BP, with M mice appearing more sensitive. Our results may suggest increased sensitivity to aldosterone in the XX versus XY genotypes.

Previously, we identified a predominant role for the alpha isoform of calcineurin (CnAα) in normal kidney development and function. However, many experiments were limited by failure to thrive and early lethality of CnAα knockout mice. Recently, we reported the rescue of CnAα −/− mice by dietary compensation for defective salivary enzyme secretion. We now provide the first report of kidney anatomy and function in adult knockout mice. The data show that despite comparable body mass, kidney size is reduced and GFR is lower in null mice. In additional, although total glomerular number is unchanged, a significant proportion of glomeruli are abnormal. Examination of the protein expression of major renal sodium transporters, channels, and exchangers reveals modest changes in proximal tubule transporters, but substantial (40–60%) decreases in the aldosterone‐sensitive Na‐Cl cotransporter (NCC), the α‐subunit of the epithelial sodium channel (ENaC), and the 70‐Da band of γ‐ENaC. Null mice also show decreased urinary potassium and hyperkalemia suggesting impaired collecting duct function. These findings are consistent with clinical observations of aldosterone resistance with use of calcineurin inhibitors and provide new experimental evidence that, in addition to glomerular development, CnAα plays a role in sodium and potassium handling by the distal nephron.