Long-term effects of intracerebroventricular insulin microinjection on renal sodium handling and arterial blood pressure in rats

Long-term exercise attenuates blood pressure responsiveness and modulates kidney angiotensin II signalling and urinary sodium excretion in SHR

“…This indirect approach allowed repeated measurements with a close correlation (correlation coefficient = 0.975), compared with direct intra-arterial recording. 22,23 The mean of three consecutive readings represented the blood pressure.…”

“…At the end of the experiment, blood samples were drawn through the tail vein or cardiac puncture in anaesthetised rats and urine and plasma samples were collected for analysis. [22][23][24] …”

“…Creatinine clearance was used to estimate glomerular filtration rate (GFR) and lithium clearance (C Li ) was used to assess proximal tubule output. [21][22][23][24] Fractional sodium excretion (FE Na ) was calculated as C Na /C Cr × 100, where C Na is sodium clearance and C Cr is creatinine clearance. The fractional proximal (FEP Na ) and post-proximal (FEPP Na ) sodium excretion were calculated as C Li /C Cr × 100 and C Na /C Li × 100, respectively.…”

Consequences of cerebroventricular insulin injection on renal sodium handling in rats: effect of inhibition of central nitric oxide synthase

“…Male Wistar-Hannover rats (250-320 g) were randomly assigned to five groups: a) icv 0.15 M NaCl-injected (control) rats (N = 10), b) icv dose-response insulin-injected rats (N = 10), c) rats injected icv with 60 µg L-NAME in combination with 0.15 M NaCl (N = 10) or d) with insulin (N = 10), and e) subcutaneously (sc) insulin-injected rats (N = 5). The animals were chronically instrumented with an icv guide cannula (17,19) and kept in individual metabolic cages under controlled temperature (25°C) and lighting conditions (7:00 to 19:00 h), with free access to tap water and standard laboratory rodent chow.…”

“…Although it has been shown that the peripheral action of insulin reduces urinary sodium excretion, suggesting an attractive reciprocal link between the renal effect of insulin, urinary sodium excre-www.bjournal.com.br Braz J Med Biol Res 42 (12) 2009 tion and the development or maintenance of hypertension, studies have indicated that acute intracerebroventricular (icv) insulin injection significantly decreases both blood pressure and heart rate, with corresponding decreases in renal sympathetic nerve activity in anesthetized rats (15,16). Our laboratory recently showed that centrally administered insulin produced a dose-related increase in the urinary output of sodium, which was abolished by bilateral renal denervation (17) and cerebroventricular streptozotocin administration in rats (18) and that the response was significantly enhanced in long-term icv insulin-pretreated animals compared to control (19). On the other hand, Shankar et al (20) have reported that acute systemic administration of high doses of N Gmonomethyl-L-arginine, a competitive inhibitor of nitric oxide (NO) synthase, results in marked insulin resistance, hyperglycemia, defective insulin secretion, and hypertension.…”