WILLIAM F. FRIEDMAN 
741 
2.0 
SHEEP 
SWINE 
1.6 
? 12 
(r. 
X 
X 
Q. 
UJ 
a. 
o 
z 
o 0.8 
< 
Q 
IE 
< 
0.4 
: 
-J 
% 
* 
P<O.OOI 
P<O.OOI 
N.S. 
FETUS <3 DAYS >3 DAYS 
ADULT 
Figure 8. — Myocardial norepinephrine concentrations 
at different stages of development in the lamb and 
sheep. Horizontal bars : mean values. 
2.0 
1.6- 
I .2 
X 
UJ 0 8 
O 
2 0.4 
ON ±001 
0 18 t 0 02 
0 35 10 03 
069 + 007 
0841026 
093 1 012 
0861 018 
104 1015 
• 
• 
• 
• 
• 
• 
• 
• 
• 
A' 
A 
• 
• 
• 
• 
• 
• 
• 
• 
• 
• 
LATE 
TERM 
2 DAY 
1 WEEK 
2 WEEK 
3 WEEKS 
4 WEEKS 
12 WEEKS 
lYEAR 
Figure 9. — Gradual increase with advancing age in 
the myocardial norepinephrine stores in the rabbit. 
Mean values are joined by the dashed line. 
FETUS 
I DAY 
I MONTH 
Figure 10. — Myocardial norepinephrine concentrations 
at different stages of development of the swine. The 
fetal values were obtained within 2 weeks of term. 
Horizontal bars: mean values. 
In contrast to norepinephrine and the intra- 
neuronal enzymes, tyrosine hydoxylase and 
monoamine oxidase, catachol-o-methyl transfer- 
ase metabolizes norepinephrine outside the 
nerve only. The activity of catachol-o-methyl 
transferase was determined by measuring the 
14C-normetanephrine formed from norepine- 
phrine and 14C-S-adenosylmethionine in the 
presence of divalent cations.^^ The activity of 
this enzyme v^as significantly higher in fetal 
than in adult myocardium (Figure 14) and sig- 
nificant inverse relationships were evident 
when the catachol-o-methyl transferase activity 
was correlated with cardiac norepinephrine 
concentration, tyrosine hydroxylase activity, 
and monoamine oxidase activity. 
All of the above biochemical observations are 
compatible with the concept that a significant 
increase in the magnitude of sympathetic inner- 
vation occurs post-natally. 
