Myocardial Catecholamines and Biosynthetic Enzymes in Various Heart Diseases of Man

Abstract

In a comparative study samples excised from a standard site of right auricular tissue during open heart surgery were assessed for their noradrenaline (NA) content as well as for their tyrosine hydroxylase (TH) and dopamine-β-hydroxylase (DBH) activities. In a total of 55 adult patients representing four different groups of heart diseases the NA contents were as follows: in ischaemic heart disease (IHD) 2.51 ±0.71 (μg/g wet tissue (mean±SD, n=19), in left-sided valvular heart disease (VHD) 1.78±0.79 (n = 10), in uncomplicated atrial septal defect (ASD) 1.33±0.70 (n=14), and in congestive heart failure (CHF) 0.64±0.34 (n= 12). The NA content was significantly higher in the IHD group than in the three other groups. The results of a corresponding fluorescence histochemical study supported the above findings. Both the TH and DBH activities were highest in the IHD group (TH 0.48 ±0.16 and DBH 2.33 ±0.92 nmoles×g−1 ×min−1) although the differences were signifiant only when compared with the ASD (TH 0.30±0.15, DBH 1.46±0.90) and the CHF (TH 0.19±0.11, DBH 0.90±0.58) group. In the whole material there was a significant positive correlation between the NA content and the TH and the DBH activities. The exact cause of the NA depletion in the failing heart is not clear. A number of factors may be involved including depressed synthesis and impaired neuronal uptake and storage. In IHD the myocardial NA content and the activities of the biosynthetic enzymes are relatively high at least when compared with those in ASD and CHF. This possibly reflects an accentuated adrenergic tone and NA turnover in IHD.