Betaine Alters the Interplay of the Adenosine and NO Systems in the Control of Renal Regional Haemodynamics and Excretion in Diabetic Female Rats

We showed recently that the adenosine system and nitric oxide (NO) can interact differently in the control of renal function in normoglycaemia (NG) versus streptozotocin-induced diabetes (DM). Herein, we investigated if this relationship is modulated by dietary betaine (Bet, food compound possessing antioxidant and anti-inflammatory properties), to examine if adenosine receptor signalling in NG and DM females is altered by chronic Bet supplementation. The effects of intravenous infusion of theophylline, non-selective adenosine receptor antagonist, were examined in anaesthetised Sprague–Dawley female rats, pretreated for 2 weeks with Bet alone or combined with 4-day NO synthesis blockade with L-NAME (Bet + L-NAME). Renal blood flow (RBF, ultrasound artery probe), perfusion of the cortex, outer (OM-BF) and inner medulla (IM-BF; laser-Doppler technique), and tissue NO signal (selective electrode) were determined along with renal excretion. Bet and Bet + L-NAME decreased baseline RBF irrespective of glycaemia, whereas Bet lowered (NG) or elevated (DM) basal OM-BF; Bet + L-NAME treatment abolished these effects. Baseline sodium excretion decreased after Bet and Bet + L-NAME in NG only. Bet modified theophylline effects: IM-BF was lowered in DM rats, while tissue NO changes shown in the control were modified: NO increased in NG and decreased in DM. In NG, these effects were abolished by Bet + L-NAME. Bet pretreatment did not alter diuresis, natriuresis and kaliuresis, but after Bet + L-NAME these parameters increased (NG) or decreased (DM). Dietary Bet has the potential to affect renal medullary blood circulation; however, the eventual effect depends on glycaemia. Bet can modify renal functional changes induced by the interplay of the adenosine and NO systems, both in rats with normoglycaemia and streptozotocin diabetes.