Abstract 499: Renal Endocannabinoids in Salt-Sensitive Hypertension of SHR

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Recent evidence suggests that endocannabinoids (ECs) acting on two major cannabinoid receptors (CB1 and CB2) regulate blood pressure and cardiovascular and renal function in health and disease. However, there is no evidence of the role of ECs in the salt-induced renal damage in hypertensive subjects. In the present study we investigated changes in the content of two major ECs, 2-arachidonoylglycerol (2-AG) and anandamide (N-arachidonoylethanolamine), and related functional changes in the kidneys of spontaneously hypertensive rats (SHR) in response to increased dietary salt intake. Male SHRs were given an 8% salt diet (HS; n=7), while their age-matched controls (C; n=7) received standard chow for 5 weeks. ECs were measured by UPLC/MS-MS methods on Applied Biosystems Mass Spectrometry Systems. After 5 weeks on a high salt diet, renal 2-AG (4.29 ± 0.40 vs. 3.32 ± 0.17 ng/mg; p<0.05) but not anandamide (2.12 ± 0.17 vs. 2.27 ± 0.07 pg/mg) increased in the salt-loaded SHR. Dietary salt excess increased mean arterial pressure (203 ± 5 vs. 171 ± 7 mmHg; p<0.05), urinary protein excretion (159 ± 37 vs. 22 ± 2 mg/day), and significantly decreased renal blood flow measured by flow probe (2.93 ± 0.55 vs. 6.67 ± 0.56 ml/min/mg; p<0.05) and glomerular filtration rate assessed by creatinine clearance (1.15 ± 0.14 vs. 1.77 ± 0.08 ml/min; p<0.05). Our previous study showed a reduction in CB1 receptor mRNA while CB2 receptor gene expression was increased in the kidney of salt-loaded SHR. Together these results suggest that alterations in renal ECs may play a significant role in the development of renal injury due to high dietary salt intake.

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