Plasma noradrenaline in Goldblatt models of renovascular hypertension in the rat, before and after surgical reversal.

Plasma noradrenaline (NA), blood pressure (BP) and heart rate (HR) were measured simultaneously in conscious rats under basal conditions in the early phase (4-6 weeks) of one-kidney, one-clip hypertension (1K1C), in the early (4-6 weeks) and chronic (greater than 16 weeks) phases of the two-kidney, one-clip model (2K1C) and in age-matched loose clip control animals before and 2 days after unclipping. The elevated BP in all three hypertensive groups fell to normal after unclipping, whereas removal of the constricting clip in loose clip controls had no effect on BP. Plasma NA was elevated in 1K1C hypertension (P less than 0.05) and fell slightly but non-significantly on unclipping. However, in the early phase of 2K1C hypertension plasma NA was unaltered before and rose significantly (P less than 0.05) after unclipping. Plasma NA did not change with unclipping in the chronic phase of 2K1C hypertension and was not different from controls. Unclipping loose clip control animals produced no change in plasma NA. Changes in HR on unclipping followed a similar pattern to changes in plasma NA: changes in the two variables were significantly correlated in all three models (1K1C: r = 0.61, P less than 0.005; early 2K1C: r = 0.45, P less than 0.05; chronic 2K1C: r = 0.62, P less than 0.01). However, BP was only correlated with plasma NA in 1K1C hypertension (r = 0.49, P less than 0.02) and not in either phase of the 2K1C model. There was also a highly significant correlation between HR and plasma NA in 1K1C hypertension (r = 0.71, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)