1. The long-term effects of sinoaortic
denervation on the development of
left ventricular hypertrophy (assessed by the measurement of the ratio (R): heart weight/total
body weight and LVT: left ventricular thickness), myocardial beta-
adrenergic receptivity (measured by [125I]-
cyanopindolol binding and
adenylate cyclase activity) and plasma
catecholamine levels (measured by h.p.l.c.) were investigated in three groups of dogs: normotensive controls (group 1), dogs made hypertensive by sinoaortic
denervation and evaluated 1 (group 2) and 18 months (group 3) later. 2.
Noradrenaline (NA) and
adrenaline (A) plasma levels were 461 +/- 54 and 85 +/- 45 pg ml-1 in controls, 861 +/- 185 and 191 +/- 23 pg ml-1 in group 2 (P less than 0.05). They were normal in group 3 (426 +/- 132 and 110 +/- 16 pg ml-1). 3. R and LVT values were significantly (P less than 0.05) higher in sinoaortic denervated dogs (R = 7.7 +/- 0.1 and 7.8 +/- 0.2; LVT = 13.6 +/- 1.3 and 14.2 +/- 0.9 mm in groups 2 and 3 respectively) than in normotensive dogs (group 1: R = 6.7 +/- 0.1, LVT = 9.3 +/- 0.8 mm). 4. In group 1, the total number of beta-
adrenoceptors (Bmax) was 37 +/- 11 and 29 +/- 6 fmol mg-1
protein in the left ventricle (LV) and right auricle (RA) respectively. In group 2, Bmax was significantly lower (10 +/- 3 in LV and 13 +/- 2 fmol mg-1
protein in RA, P less than 0.05) than in group 1. There was no difference between group 1 and group 3 (37 +/- 3 fmol mg-1 prot in LV and 31 +/- 3 fmol mg-1
protein in RA). 5. The percentage of beta 1-adrenoceptors was 82 +/- 4 in LV and 75 +/- 5 in RA in group 1. It was significantly lower (P less than 0.05) in groups 2 (LV: 33 +/- 6 and RA: 33 +/- 5) and 3 (LV: 59 +/- 3 and RA: 55 +/- 4). 6. Basal values of
adenylate cyclase activity in LV significantly decreased after sinoaortic
denervation.7. These data show that sinoaortic
denervation is associated with
left ventricular hypertrophy which appears early (1 month) and persists until 18 months despite the normalization of plasma
catecholamine levels. The total number of myocardial beta-
adrenoceptors is closely related to
catecholamine levels but a selective decrease in beta 1-adrenoceptors is observed during
cardiac hypertrophy. The fall in basal
adenylate cyclase activity suggests that
cardiac hypertrophy is associated with an impairment of transmembrane signalling.