title: Altered pressure-natriuresis in obese Zucker rats.
abstract: It has not been examined whether the pressure-natriuresis response is altered in the insulin-resistant condition. Furthermore, despite an important role of nitric oxide (NO) in modulating pressure-natriuresis, no investigations have been conducted assessing the renal interstitial NO production in insulin resistance. The present study examined whether pressure-natriuresis was altered in insulin-resistant obese Zucker rats (OZ) and assessed the cortical and medullary nitrate/nitrite (NOx) levels with the use of the renal microdialysis technique. In OZ, serum insulin/glucose ratio (23.0+/-4.0x10(-8), n=9) and blood pressure (119+/-3 mm Hg) were greater than those in lean Zucker rats (LZ; 7.0+/-1.9x10(-8) and 103+/-4 mm Hg, n=9). The pressure-natriuresis curve in OZ was shifted to higher renal perfusion pressure (RPP), and the slope was blunted compared with that in LZ (0.073+/-0.015 vs 0.217+/-0.047 microEq/min kidney weight/mm Hg, P<0.05). The basal renal NOx level was reduced in OZ (cortex, 4.032+/-0.331 micromol/L; medulla, 4. 329+/-0.515 micromol/L) compared with that in LZ (cortex, 7.315+/-1. 102 micromol/L; medulla: 7.698+/-0.964 micromol/L). Furthermore, elevating RPP increased the medullary NOx in LZ, but this pressure-induced response was lost in OZ. Four-week treatment with troglitazone, an insulin-sensitizing agent, improved hyperinsulinemia, systemic hypertension, and basal renal NOx levels (cortex, 5.639+/-0.286 micromol/L; medulla, 5.978+/-0.284 micromol/L), and partially ameliorated the pressure-natriuresis curves; the slope of pressure-natriuresis curves and elevated RPP-induced NOx, however, were not corrected. In conclusion, our study suggests that insulin resistance is closely associated with abnormal pressure-natriuresis and hypertension. These deranged renal responses to insulin resistance are most likely attributed to impaired medullary NO production within the medulla.
authors.affiliation: Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Fujiwara
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.forename: H
authors.initials: H
authors.lastname: Matsuda
authors.forename: E
authors.initials: E
authors.lastname: Kubota
authors.forename: M
authors.initials: M
authors.lastname: Honda
authors.forename: Y
authors.initials: Y
authors.lastname: Ozawa
authors.forename: T
authors.initials: T
authors.lastname: Saruta
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure; D001835:Body Weight; D004231:Diuresis; D005919:Glomerular Filtration Rate; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D007668:Kidney / Q000378:metabolism / Q000502:physiology* / Q000503:physiopathology; D007672:Kidney Cortex / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D009318:Natriuresis; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009765:Obesity / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D051381:Rats; D011924:Rats, Zucker; D012039:Regional Blood Flow; D012079:Renal Circulation; D013851:Thinness
chemical_list: D001786:Blood Glucose; D007328:Insulin; D009566:Nitrates; D009573:Nitrites