PP.11.18

Abstract

Objective: Evidences indicate that in addition to long term regulation of blood pressure, in the kidney resides the initial trigger for the development of hypertension. Altered capacity of the kidney to excrete sodium and water in relation to intake has been proposed as a basic mechanism of initiating hypertension. Betaine is one of the major organic osmolytes and the upregulation of its betaine/gamma-aminobutyric acid transporter (BGT1) in the renal medulla is related to high extracellular tonicity and urinary osmolality. Design and method: The present study investigated the abnormalities in water and sodium balance and osmoregulation in a model of polygenic multifactorial arterial hypertension, the spontaneously hypertensive rats (SHR, n = 58) and compared with their normotensive controls Wistar Kyoto (WKY, n = 46 from their prehypertensive phase (4 weeks of age) until the development hypertension and of organ damage (28–30 weeks of age). Rats were housed in metabolic cages to monitor water and salt balance parameters at the age of 4–5, 14–16 and 28–30 weeks of age. Results: No difference of blood pressure (both indirectly tail cuff method and invasively, as well heart rate, body weight, serum sodium, potassium and creatinine levels) was measured at the age of 5 weeks of age between SHR and WKY. Daily urinary volume was reduced in prehypertensive SHR as compared to WKY (-36 %, p Conclusions: All these results suggest in prehypertensive SHR an early positive balance of water before sodium balance alteration.