Real-time observation of glomerular hemodynamic changes in diabetic rats: effects of insulin and ARB.
BACKGROUND
The progression of diabetic nephropathy is closely related to disturbances in glomerular hemodynamics, such as glomerular hypertension and/or hyperperfusion. The aim of this study was to observe and to analyze glomerular hemodynamics in rats with diabetes mellitus (DM) in vivo using confocal laser scan microscopy (CLSM). We also examined the effects of candesartan cilexetil (TCV-116), a selective angiotensin II type 1 receptor blocker (ARB), on glomerular hemodynamics in DM.


METHODS
Munich-Wistar rats were divided into six groups: (1) four-day control; (2) four-day DM; (3) 28-day control; (4) 28-day DM; (5) DM treated with insulin; (6) DM treated with TCV-116. The kidney-to-body weight ratio, glomerular volume, and proteinuria were estimated. Glomerular hemodynamic changes were observed using CLSM and renal expression of endothelial nitric oxide synthase (eNOS), and neuronal nitric oxide synthase (nNOS) was evaluated by immunofluorescence.


RESULTS
The kidney-to-body weight ratio, glomerular volume, the diameters of afferent arterioles (AA) and efferent arterioles (EA), erythrocyte velocities within glomeruli, and volume flow in glomerular capillary loops in four-day DM were significantly higher than in control rats, and increases were even more pronounced in the 28-day DM. TCV-116 treatment ameliorated all these findings and significantly decreased proteinuria, but there was no effect on the blood glucose level. On the other hand, insulin treatment was followed by normalization of all these changes induced in DM. Enhanced renal expression of eNOS in DM was suppressed when treated with either TCV-116 or insulin, while expression of nNOS was unaltered among the four groups.


CONCLUSIONS
This imaging procedure allowed us to evaluate glomerular microcirculation in vivo, including the diameters of AA and EA, erythrocyte velocity, and volume flow. DM significantly induced glomerular hemodynamic alteration and renal hypertrophy. DM treated with either insulin or ARB ameliorated these changes. This study shows that progress in imaging technology promises to make major contributions to revealing the involvement of hemodynamic changes in glomerular diseases, aiding prognosis and the monitoring of therapeutic effects, as well.
Li
Bing
B
Department of Cellular Physiology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Yao
Jian
J
Kawamura
Kazuko
K
Oyanagi-Tanaka
Yukiko
Y
Hoshiyama
Mari
M
Morioka
Tetsuo
T
Gejyo
Fumitake
F
Uchiyama
Makoto
M
Oite
Takashi
T
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000473:pathology; D001562:Benzimidazoles / Q000494:pharmacology*; D001713:Biphenyl Compounds; D001783:Blood Flow Velocity; D002196:Capillaries / Q000503:physiopathology; D003921:Diabetes Mellitus, Experimental / Q000473:pathology / Q000503:physiopathology*; D004912:Erythrocytes; D005455:Fluorescent Antibody Technique; D006439:Hemodynamics / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D007678:Kidney Glomerulus / Q000098:blood supply* / Q000201:enzymology / Q000473:pathology; D008297:Male; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D009929:Organ Size; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow; D012079:Renal Circulation / Q000187:drug effects*; D013777:Tetrazoles / Q000494:pharmacology*
D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D007328:Insulin; D009419:Nerve Tissue Proteins; D013777:Tetrazoles; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496316:Nos3 protein, rat; C081643:candesartan