EFFECT OF NITRITE ON BLOOD-PRESSURE IN ANESTHETIZED AND FREE-MOVING RATS

The effect of nitrite on blood pressure and heart rate was studied in anaesthetized (non-telemetric method) and free-moving rats (biotelemet ry system). In anaesthetized rats, NaNO2 (10-1000 mu mol/kg), infused over 5 min, induced a dose-related decrease in blood pressure. The max imal decrease in mean arterial blood pressure (MAP), caused by 1000 mu mol/kg NaNO2 and measured 15 min after infusion was 55.9 +/- 3.2% (n = 3). After NaNO2 infusion, in the plasma, rapid conversion of nitrite into nitrate was observed. However, sodium nitrate (NaNO3, 100 mu mol /kg) did not decrease blood pressure and there was no conversion of ni trate into nitrite. Free-moving rats received KNO2 which was added to drinking water (36 mmol/litre) for a period of 3 days. KNO2 decreased the MAP and increased the heart rate during the rat's activity phase a t night but not during their resting phase in the day. An equal concen tration of potassium (KCl, 36 mmol/litre added to drinking water) for 3 days did not decrease blood pressure. It is concluded that nitrite d ecreases blood pressure in rats, which probably induces, by renin-angi otensin system activation, hypertrophy of the adrenal zona glomerulosa . (C) 1997 Elsevier Science Ltd.