Supplementary Table 2 Pharmacokinetic parametersa of irinotecan and its main active metabolite SN-38 when irinotecan was administered as a 1.5-h intravenous infusion (100 mg/m2) alone on cycle 1 day 1 or in combination with veliparib on cycle 2 day 8

Supplementary Figure S3. pNBS1 staining post-combination treatment is limited to tumor cells.

Supplementary Figure S4. Assessment of pNBS1 in the exploratory multiplex immunofluorescence assay.

Supplementary Figure S1. Study schema.

Supplementary Table 1 Pharmacokinetic parametersa of veliparib and its main metabolite (A- 925088) when veliparib was given orally alone on cycle 2 day -1 or in combination with irinotecan on cycle 2 day 8

Supplementary Figure S2. Dose-exposure relationships.

Nitric oxide prevents hypertension yet enhances proximal tubule Na+ reabsorption. Nitric oxide synthase is inhibited by asymmetric dimethylarginine (ADMA) that is metabolized by dimethylarginine dimethylaminohydrolase (DDAH) whose type 1 isoform is expressed abundantly in the proximal tubule (PT). We hypothesize that ADMA metabolized by DDAH-1 inhibits fluid reabsorbtion (Jv) by the proximal tubule. S2 segments of the PT were microperfused between blocks in vivo to assess Jv in anesthetized rats. Compared with vehicle, microperfusion of ADMA or Nω-nitro-l-arginine methyl ester (l-NAME) in the proximal tubule reduced Jv dose dependently. At 10-4 mol/l both reduced Jv by ~40% (vehicle: 3.2 ± 0.7 vs. ADMA: 2.1 ± 0.5, P < 0.01 vs. l-NAME: 1.9 ± 0.4 nl·min-1·mm-1, P < 0.01; n = 10). Selective inhibition of DDAH-1 in rats with intravenous L-257 (60 mg/kg) given 2 h before and L-257 (10-5 mol/l) perfused in the proximal tubule for 5 min reduced Jv by 32 ± 4% (vehicle: 3.2 ± 0.5 vs. L-257: 2.2 ± 0.5 nl·min-1·mm-1; P < 0.01) and increased plasma ADMA by ≈50% (vehicle: 0.46 ± 0.03 vs. L-257: 0.67 ± 0.03 µmol/l, P < 0.0001) without changing plasma symmetric dimethylarginine. Compared with nontargeted control small-interference RNA, knock down of DDAH-1 in mice by 60% with targeted small-interference RNAs (siRNA) reduced Jv by 29 ± 5% (nontargeted siRNA: 2.8 ± 0.20 vs. DDAH-1 knockdown: 1.9 ± 0.31 nl·min-1·mm-1, P < 0.05). In conclusion, fluid reabsorption in the proximal tubule is reduced by tubular ADMA or by blocking its metabolism by DDAH-1. L-257 is a novel regulator of proximal tubule fluid reabsorption.

The University System of Maryland's Louis Stokes Alliance for Minority Participation (LSAMP) shares the United Nations' Sustainable Development Goals (SDGs) with underrepresented minority (URM) STEM students. In July 2018, faculty and students from three institutions within the USM LSAMP worked with World SPEED - the Student Platform for Engineering Education Development, to share the UN's SDGs during the 2018 conference of the Latin and Caribbean Consortium of Engineering Institutions (LACCEI) in Lima, Peru. Students from the US, Peru, Colombia, Brazil, and other countries were exposed to the SDGs in both English and Spanish through World SPEED's SDG-focused panel and team-based exercises. The exercises allowed students, working in teams that mixed countries (and languages), to develop solutions to challenges based on the SDGs. Students discussed research in the context of the SDGs, such as SDG 3: Better health solutions for people around the world, SDG 4: Global quality education, SDG 5: Gender equality, and SDG 7: Affordable and clean energy solutions that will allow humans to generate clean, reusable power. This project allowed URM students from the US to consider engineering in the context of "peace," contributing to STEM identity, retention, and utilization of their talents for a peaceful purpose.

Abstract Purpose: PARP is essential for recognition and repair of DNA damage. In preclinical models, PARP inhibitors modulate topoisomerase I inhibitor–mediated DNA damage. This phase I study determined the MTD, dose-limiting toxicities (DLT), pharmacokinetics (PK), and pharmacodynamics (PD) of veliparib, an orally bioavailable PARP1/2 inhibitor, in combination with irinotecan. Experimental Design: Patients with advanced solid tumors were treated with 100 mg/m2 irinotecan on days 1 and 8 of a 21-day cycle. Twice-daily oral dosing of veliparib (10–50 mg) occurred on days 3 to 14 (cycle 1) and days −1 to 14 (subsequent cycles) followed by a 6-day rest. PK studies were conducted with both agents alone and in combination. Paired tumor biopsies were obtained after irinotecan alone and veliparib/irinotecan to evaluate PARP1/2 inhibition and explore DNA damage signals (nuclear γ-H2AX and pNBS1). Results: Thirty-five patients were treated. DLTs included fatigue, diarrhea, febrile neutropenia, and neutropenia. The MTD was 100 mg/m2 irinotecan (days 1 and 8) combined with veliparib 40 mg twice daily (days −1–14) on a 21-day cycle. Of 31 response-evaluable patients, there were six (19%) partial responses. Veliparib exhibited linear PK, and there were no apparent PK interactions between veliparib and irinotecan. At all dose levels, veliparib reduced tumor poly(ADP-ribose) (PAR) content in the presence of irinotecan. Several samples showed increases in γ-H2AX and pNBS1 after veliparib/irinotecan compared with irinotecan alone. Conclusions: Veliparib can be safely combined with irinotecan at doses that inhibit PARP catalytic activity. Preliminary antitumor activity justifies further evaluation of the combination. Clin Cancer Res; 22(13); 3227–37. ©2016 AACR.

Abstract Background: The nuclear enzyme PARP is essential in recognition and repair of DNA damage. Preclinical evidence suggests that PARP inhibitors work as sensitizing agents for DNA-damaging agents such as irinotecan. Veliparib is an orally bioavailable PARP 1 and 2 inhibitor. This expansion to a phase I study, which demonstrated veliparib reduces PAR levels in tumor after irinotecan exposure, was conducted to assess the safety, tolerability and preliminary anti-tumor activity of the combination of veliparib and irinotecan in triple negative breast cancer (TNBC) patients (pts), as well as to apply next generation sequencing technologies to define a signature of response. Methods: Pts were enrolled to two breast cancer cohorts: (1) TNBC, germline BRCA-mutant positive and (2) TNBC, non-BRCA mutated (wt). Eligibility included performance status 0-2; ≥ age 18; adequate bone marrow, hepatic and renal function. Cycles were 21 days. Irinotecan was given i.v. 100 mg/m2 over 90 min on Days 1 and 8. Twice daily (BID) oral dosing of 40 mg veliparib occurred Days 2-15 (Cycle 1) and Days 1-15 (subsequent cycles) followed by a 6-day rest. Tumor biopsies were collected at baseline, 4-6 hours after the first dose of irinotecan (day 1) and the combination (day 8) in cycle 1. Whole exome and transcriptome sequencing was performed using both normal and tumor tissue. Circulating tumor cells (CTC) were evaluated using the CellSearch platform. Results: 24 TNBC pts were enrolled, with 20 pts treated and evaluable for response (8 germline BRCA-mutation positive, 10 non-BRCA mutated, 2 suspected deleterious). Median age was 51 (range 31-63). Median number of prior treatments was 4 (range 1-7). Most frequent drug-related toxicities included: leukopenia (60%), neutropenia (60%), nausea (55%), diarrhea (40%), fatigue (40%), anemia (30%), and vomiting (30%). Best responses were as follows: Germline BRCA-mutant positive 7/8 PR (88%; median number of days on study = 330; range 148-594 days), 1/8 PD (12%); suspected deleterious 2/2 PD (100%); non-BRCA mutated 7/10 SD (70%; median number of days on study = 70; range 42-98 days), 3/10 PD (30%). Exploratory molecular profiling has been performed in a subset of these pts and the results will be presented. EpCAM+ CTC numbers were evaluable in 11 of 22 enrolled pts, and nuclear γH2Ax+, a pharmacodynamic biomarker of DNA damage, was identified in a fraction of CTCs from all 11 of these pts. Conclusions: Veliparib in combination with irinotecan was safe and tolerable in TNBC pts. Although the cohort in this trial is small, the preliminary response rate of 88% in pts with germline BRCA mutation is encouraging and higher than that historically reported with PARP inhibitor monotherapy in this population. Deep molecular profiling among BRCA mutant carriers will be validated in a larger, independent cohort to define potential biomarkers of response. Support: NCI U01-CA062487, NCI U01-CA062490, Komen KG120001, NCI R21-CA135572, and HHSN261200800001E. Citation Format: Patricia M. LoRusso, Sara M. Tolaney, Shukmei Wong, Ralph E. Parchment, Robert J. Kinders, Lihua Wang, Jessica Aldrich, Alice Chen, Diane Durecki, Scott A. Boerner, Tina Guthrie, Adam Bowditch, Lance K. Heilbrun, Mary Jo Pilat, David Craig, Dongpo Cai, Tracy Bell, John Carpten, Geoffrey Shapiro. Combination of the PARP inhibitor veliparib (ABT888) with irinotecan in patients with triple negative breast cancer: Preliminary activity and signature of response. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT325. doi:10.1158/1538-7445.AM2015-CT325

Background: Proximal tubule (PT) fluid reabsorption (Jv) is diminished by knockout of NOS-I or III. ADMA is an endogenous inhibitor of NOS, but its effects on tubular function are unknown. ADMA is degradated by DDAH whose type 1 isoform (DDAH-1) is richly expressed in the PT. SNIPs of DDAH-1 predict the decline of GFR in chronic kidney disease (CKD). Hypothesis: that DDAH-1 metabolizes ADMA in the PT thereby reducing its plasma concentration and enhancing Jv. Methods: Jv was measured in anesthetized rats and mice in S2 segments of the PT by direct in vivo micropuncture and microperfusion of artificial tubular fluid (ATF). Results: Addition of L-257 (10 -4 M; DDAH-1 inhibitor) vs vehicle to ATF perfusing the PT of rats for 10 mins did not affect Jv (3.4 ± 0.20 vs 3.1±0.39 nl/min/mm). However, a bolus i.v. injection (60mg/kg) of L-257 2hrs before and 10 mins of PT perfusion significantly (P< 0.005) reduced Jv by 33% to 2.3±0.17 nl/min/mm and increased plasma ADMA (systemic Veh: 0.46 ± 0.030 vs. systemic L-257: 0.67 ± 0.029 μmol/l; P < 0.0001) without changing SDMA. Microperfusion of ADMA (10 -4 M) or L-NAME (10 -4 M) in rats both reduced Jv significantly by >40% to 2.0±0.24 and 1.8±0.22 nl/min/mm, respectively (P<0.05). An IV 1 ml bolus of saline containing Transit and siRNA targeted to DDAH-1 (hydrodynamic in vivo gene silencing in mice) three days later reduced Jv significantly by 36% compared to scrambled siRNA (2.2 ± 0.16 vs 1.4 ± 0.26 nl/min/mm; P<0.05). Surprisingly, PT cell-specific DDAH-1 knockdown in mice did not affect Jv significantly compared to wild type (PTC-D1WT: 1.7 ± 0.21 vs PTC-D1KO: 2.0 ± 0.15). Conclusions: PT fluid reabsorption is regulated by ADMA and its tubular metabolism by DDAH-1. The two-hour delay for L-257 to diminish Jv likely was required for accumulation of sufficient tubular ADMA to impair PT reabsorption. Whereas systemic DDAH-1 gene knockdown in mice was as effective as systemic DDAH-1 blockade with L-257 in rats in reducing Jv in the PT, lifelong deletion of PT DDAH-1 was ineffective, suggesting robust adaptive mechanisms that restore PT reabsorption. Thus, L-257 is a novel regulator of PT function. SNIPs that alter DDAH-1 in the PT may change tubular function and thereby contribute to CKD progression.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Background: Sapacitabine is an orally administered nucleoside analogue; the active metabolite, CNDAC (2′-C-cyano-2′-deoxy-1-β-D-arabino-pentofuranosylcytosine), generates single-strand DNA breaks that are converted to double-strand DNA breaks (DSBs) during subsequent replication, resulting in cell death if unrepaired. Repair of CNDAC-induced DSBs is dependent on the homologous recombination (HR) repair pathway. Depletion or inhibition of components of the HR pathway (including ATM, BRCA1/2, Rad 51, and XRCC3) greatly sensitizes tumor cell lines to CNDAC-induced cell death in vitro . Seliciclib is an orally bioavailable inhibitor of cyclin-dependent kinases (CDKs) 2, 7 and 9. CDK2 has been shown to participate in DNA repair and to be a therapeutic target in BRCA-deficient cancers. Seliciclib inhibits DSB repair, and also reduces BRCA1 and BRCA2 mRNA levels in cancer cell lines, sensitizing tumor cells to CNDAC. This phase I study evaluates sequential sapacitabine and seliciclib. Methods: Dose escalation was conducted in patients with incurable solid tumors and adequate organ function with sapacitabine bid x 7 consecutive days (d1-7), seliciclib bid x 3 consecutive days (d8-10) followed by 11 days of rest. At least 3 patients were evaluated per dose level. MTD was the highest dose level at which less than one-third of at least 6 patients experienced cycle 1 DLT. Skin biopsies were obtained to assess DNA damage following sapacitabine (d8 vs pre-treatment) and further augmentation of DNA damage after seliciclib (d11 vs d8). Results: 38 patients were treated. The MTD is sapacitabine 50 mg bid/seliciclib 1200 mg bid. DLTs were reversible transaminase elevations and neutropenia. The most frequent adverse events (all cycles, regardless of causality) included, fatigue, abdominal pain, diarrhea, constipation, decreased appetite, nausea, vomiting, anemia, neutropenia, pyrexia, AST elevation, alkaline phosphatase elevation, creatinine elevation, hyperglycemia, hypophosphatemia, cough, and alopecia, the majority mild to moderate in intensity. Skin biopsies showed a 2.3-fold increase in γ-H2AX staining post-sapacitabine (n=16; p=0.007) and a further 0.58-fold increase post-seliciclib (n=12; p=0.069). Four confirmed PRs occurred in patients with pancreatic, breast (2 pts) and ovarian cancer, all BRCA mutation carriers, lasting 21, 78+, 36+ and 42+ weeks, respectively. SD as best response ≥= 12 weeks was observed in 8 additional patients, including two BRCA mutation carriers with ovarian and breast cancer, lasting 64 and 21 weeks, respectively. Conclusions: Sequential sapacitabine and seliciclib is safe with preliminary antitumor activity. BRCA mutation carrier status may be a potential biomarker for response across multiple tumor types. An alternative schedule with concomitant administration of sapacitabine and seliciclib is currently under evaluation. Citation Format: Geoffrey I. Shapiro, John Hilton, James M. Cleary, Sara M. Tolaney, Leena Ghandi, Eunice L. Kwak, Jeffrey W. Clark, Andrew Wolanski, Tracy Bell, John Schulz, Sheelagh Frame, Chiara Saladino, Morag Hogben, Scott J. Rodig, Judy H. Chiao, David Blake. Responses to sequential sapacitabine and seliciclib in patients with BRCA-deficient solid tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-202. doi:10.1158/1538-7445.AM2013-LB-202

Nitric oxide (NO) stimulates proximal tubule (PT) Na + and fluid reabsorption. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS) but its effects on tubular function are unknown. ADMA is metabolized by dimethylarginine dimethylaminohydrolase (DDAH) whose type 1 isoform is predominant in the PT. SNIPs of DDAH-1 predicted the rate of decline of renal function in patients with chronic kidney disease (CKD). Therefore, we tested the hypothesis that DDAH-1 metabolizes ADMA in the proximal tubule and thereby enhances PT fluid reabsorption (J v ). J v was measured in anesthetized rats by direct in vivo microperfusion and recollection of artificial tubular fluid (ATF) in S2 segments of the PT isolated between oil blocks. Addition of a selective inhibitor of DDAH-1, L-257 (10 -4 M) to ATF did not effect J v when compared to addition of vehicle (3.40.6 vs 3.10.3 nl/min/mm). However, L-257 administered as a bolus intravenous injection (60mg/kg) 2hrs before microperfusion of the PT with L-257 significantly reduced J v to 1.80.2 nl/min/mm, (P<0.05) and significantly enhanced urine flow rate (2.1±0.3 vs 9.0±1.8 μl/min; P<0.05). Microperfusion of ADMA (10 -4 M) or L-NAME (10 -4 M) into the PT both reduced J v significantly to 2.00.2 and 1.80.2 nl/min/mm, respectively (P<0.05). Rats pretreated with a rapid intravenous injection of siRNA targeted to DDAH-1 that reduced its renal mRNA expression significantly also had reduced J v (3.1±0.2 vs 2.2±6.2 nl/min/mm; P<0.05) and had a further reduction in J v with 10 -4 M ADMA added to ATF to 1.4±0.1 nl/min/mm; (P<0.005). In conclusion, PT fluid reabsorption is regulated by ADMA and its tubular metabolism by DDAH-1. The two hour delay in the effects of a bolus injection of L-257 to diminish J v indicated the time required after inhibition of DDAH-1 for accumulation of sufficient tubular ADMA to impair PT reabsorption. Thus, L-257 is a novel regulator of PT function and is a proximal tubule diuretic. SNIPs that alter DDAH-1 in the PT may change renal function and contribute to CKD progression.

Glomerular tubular balance maintains a stable fractional solute and fluid reabsorption in the proximal tubule over a range of glomerular filtration rates. The mediators of this process are unknown. We tested the hypothesis that adenosine, produced in proximal tubule cells acting on adenosine type 1 receptors (A(1)-AR) promotes Na(+) and fluid uptake and mediates glomerular tubular balance. Absolute proximal fluid reabsorption (J(v)) was measured by in vivo microperfusion in A(1)-AR knockout and wild-type mice during perfusion of the closed proximal tubule at 2-10 nl/min. J(v) increased with perfusate flow from 2-4 nl/min in both strains, but the fractional increase was lower in A(1)-AR(-/-) mice (A(1)-AR(+/+): 114% vs. A(1)-AR(-/-): 38%; P < 0.001), suggesting reduced glomerular tubular balance (GTB). At higher perfusion rates, J(v) increased modestly in both strains, indicating less GTB at higher flow. The physiological effects of reduced GTB in A(1)-AR(-/-) mice were assessed from the response to an acute volume load (1 ml/2 min). Na(+) excretion and urine flow increased 76 and 73% more in A(1)-AR(-/-) mice than A(1)-AR(+/+) over the following 30 min, accompanied by a higher proximal tubule flow (A(1)-AR(-/-): 6.9 ± 0.9 vs. A(1)-AR(+/+): 5.2 ± 0.6 nl/min; P < 0.05). The expression of the sodium-hydrogen exchanger 3 and sodium phosphate cotransporter-2 were similar between strains. In conclusion, GTB is dependent on adenosine acting on type 1 receptors in the proximal tubule. This may contribute to acute changes in Na(+) and fluid reabsorption.

This study tested the hypothesis that inducing hyperinsulinemia and hyperglycemia in dogs, by infusing glucose chronically intravenously, would increase tubular sodium reabsorption and cause hypertension. Glucose was infused for 6 days (14 mg.kg(-1).min(-1) iv) in five uninephrectomized (UNX) dogs. Mean arterial pressure (MAP) and renal blood flow (RBF) were measured 18 h/day using DSI pressure units and Transonic flow probes, respectively. Urinary sodium excretion (UNaV) decreased significantly on day 1 and remained decreased over the 6 days, coupled with a significant, sustained increase in RBF, averaging approximately 20% above control on day 6. Glomerular filtration rate and plasma renin activity (PRA) also increased. However, although MAP tended to increase, this was not statistically significant. Therefore, the glucose infusion was repeated in six dogs with 70% surgical reduction in kidney mass (RKM) and high salt intake. Blood glucose and plasma insulin increased similar to the UNX dogs, and there was significant sodium retention, but MAP still did not increase. Interestingly, the increases in PRA and RBF were prevented in the RKM dogs. The decrease in UNaV, increased RBF, and slightly elevated MAP show that glucose infusion in dogs caused a sustained increase in tubular sodium reabsorption by a mechanism independent of pressure natriuresis. The accompanying increase in PRA, together with the failure of either RBF or PRA to increase in the RKM dogs, suggests the site of tubular reabsorption was before the macula densa. However, the volume retention and peripheral edema suggest that systemic vasodilation offsets any potential renal actions to increase MAP in this experimental model in dogs.

Tubuloglomerular feedback regulation of glomerular filtration rate (GFR) is mediated by adenosine, which acts on type 1 receptors in the afferent arteriole to increase resistance. However, new findings in isolated mouse tissue suggest that adenosine also dilates the efferent arteriole, which would reinforce the ability of adenosine to reduce GFR. This new information extends the concept that adenosine acts as a paracrine agent on both afferent and efferent arterioles.

This study used 16 h/day measurement of renal blood flow (RBF) and arterial pressure (AP) to determine the role of nitric oxide (NO) in mediating the renal vasodilation caused by onset of type 1 diabetes. The AP and RBF power spectra were used to determine the autoregulatory efficiency of the renal vasculature. Rats were instrumented with artery and vein catheters and a Transonic flow probe on the left renal artery and were divided randomly into four groups: control (C), diabetes (D), control plus nitro-L-arginine methyl ester (L-NAME; CL), and diabetes plus L-NAME (DL). Mean AP averaged 90 +/- 1 and 121 +/- 1 mmHg in the D and DL groups, respectively, during the control period, and RBF averaged 5.9 +/- 1.2 and 5.7 +/- 0.7 ml/min, respectively. Respective C and CL groups were not different. Onset of diabetes (streptozotocin 40 mg/kg iv) in D rats increased RBF gradually, but it averaged 55% above control by day 14. In DL rats, on the other hand, RBF remained essentially constant, tracking with RBF in the nondiabetic C and CL groups for the 2-wk period. Diabetes did not change mean AP in any group. Transfer function analysis revealed impaired dynamic autoregulation of RBF overall, including the frequency range of tubuloglomerular feedback (TGF), and L-NAME completely prevented those changes as well. These data strongly support a role for NO in causing renal vasodilation in diabetes and suggest that an effect of NO to blunt RBF autoregulation may play an important role.

When diabetes is induced in rats that have NO synthesis blocked chronically, MAP increases significantly, and we have shown that chronic i.v infusion of α1 and β-adrenergic receptor antagonists attenuates the hypertension. This study was designed to determine the role of the renal sympathetic nerves in mediating the increase in blood pressure in uninephrectomized control (C)and denervated (D) rats. Rats in either group were pretreated with vehicle (C; n=3 and D; n=3) or L-NAME (C+L; n=3 and D+L; n=4) for ~7 days and then STZ was administered to mark the beginning of 2 weeks of Type I diabetes. Baseline MAP in C and D rats averaged 96±0.7 and 90±0.3 mmHg, and there was no change in MAP during diabetes. However, as we have shown in previous studies, MAP progressively increased at onset of diabetes in L-NAME treated rats (C+L), from the L-NAME baseline of 125±2.6 mmHg to 145±4.3 and 173±13.0 mmHg during diabetic weeks 1 and 2, respectively. Denervation lowered the L-NAME baseline to 108±0.8 mmHg and prevented the diabetes induced hypertension, with MAP averaging 112±1.5 and 120±3.2 mmHg, respectively, during diabetic weeks 1 and 2. Glomerular filtration rate (GFR) increased at the onset of diabetes in the C and D groups and this response was prevented in rats treated with L-NAME, as we have reported, and denervation prevented that effect. These data suggest that renal sympathetic activity plays an important role in the hypertensive response to the onset of diabetes in the absence of NO, and this effect is consistent with the role of renal vascular resistance and ANGII that we have reported.

1. The relationship between sodium intake and blood pressure is affected differently by changes in angiotensin (Ang) II and preglomerular resistance, and this study measured that relationship to evaluate the link between nitric oxide and blood pressure early in diabetes. 2. Rats were chronically instrumented, placed on high-sodium (HS = 12 mEq/d) or low-sodium (LS = 0.07 mEq/d) intake diets and assigned to either vehicle- (V) or Nomega-nitro-L-arginine methyl ester- (L-NAME; L) treated groups. Mean arterial pressure (MAP) was measured 18 h/day for a 6-day control and 14-day streptozotocin diabetic period in each animal. 3. The MAP of the control period averaged 95 +/- 1 and 94 +/- 1 mmHg in the LSV and HSV rats and 116 +/- 2 and 124 +/- 1 mmHg in the LSL and HSL rats, respectively (LSL vs HSL was significant at P < 0.05). Diabetes increased MAP only in the LSL and HSL rats to 141 +/- 2 mmHg and 152 +/- 2, respectively, similar to our previous reports, and those respective 25 and 28 mmHg increases were a parallel shift in the pressure natriuresis relationship. However, the apparent difference between the LSL and HSL groups when compared was a parallel of the control MAP difference. Plasma renin activity (PRA) in the control period averaged 1.5 +/- 0.5 and 8.1 +/- 1.8 ng AI/mL per h in the HSV and LSV rats, and 0.8 +/- 0.2 and 2.8 +/- 0.5 ng AI/mL per h in the HSL and LSL rats, respectively, and increased similarly by 4.6-fold in the HSL and 4.8-fold in the LSL rats during diabetes. Glomerular filtration rate (GFR) increased in the vehicle but not the L-NAME-treated groups, consistent with our previous reports. 4. Thus, the hypertension caused by the onset of diabetes in L-NAME-treated rats was not salt-sensitive. The normal modulation of PRA by salt intake and the failure of GFR to increase are consistent with our hypothesis that nitric oxide may protect against hypertension early in diabetes by preventing preglomerular vasoconstriction by AngII.