Effect of sympathectomy on axoplasmic transport of selected enzymes including MAO and other mitochondrial enzymes

In vivo labelling and axonal transport of monoamine oxidase in the rat basal ganglia using radioactive pargyline

The enzyme monoamine oxidase was labelled in the rat striatum or substantia nigra with locally injected radioactive pargyline. The binding was prevented by a pretreatment with non-radioactive pargyline, or with a combination of clorgyline and deprenyl. Most of the MAO labelled with 3H-pargyline was of the B-type, but also some MAO-A was labelled, as shown in rats pretreated with clorgyline or deprenyl separately. Seven days after the injection of (3H)-pargyline into the striatum a significant labelling was observed in the substantia nigra. This labelling was clorgyline sensitive, indicating type A MAO, and was not present when striatal neurons were destroyed with kainic acid. Labelling of the striatum following 3H-pargyline injection into the substantia nigra was also less in kainate intoxicated striata. Damage of nigral dopamine neurons with 6-hydroxydopamine did not influence the distribution of the label. Thus by using 3H-pargyline, specific labelling and axonal transport of type A MAO in striatal neurons projecting to the substantia nigra was demonstrated.

Monoamine oxidase type A: differences in selectivity towards l-norepinephrine compared to serotonin

l-Norepinephrine and serotonin have been regarded as preferential substrates for monoamine oxidase (MAO) type A. A close comparative examination of a number of tissues from different species, however, indicated the following differences. Serotonin was a more selective substrate for MAO-A, being inhibited by low concentrations (less than 10(-7) M) of the irreversible MAO-A inhibitor, clorgyline, more consistently and to a greater extent (80-100%) than was l-norepinephrine (30-85%). These serotonin-norepinephrine differences were greater in humans and other primates than in rodents. Serotonin also had a 2- to 4-fold smaller apparent Km for MAO-A than l-norepinephrine and was deaminated 2- to 5-fold more readily by MAO in vitro in most tissues. In contrast, the MAO-B in human platelets deaminated l-norepinephrine more readily than serotonin. Thus, l-norepinephrine, like dopamine, should be regarded as a substrate for both MAO-A and MAO-B in vitro. The prominent role of MAO-B in norepinephrine degradation in primates may need to be considered in interpreting laboratory and clinical studies of clorgyline and other selective MAO-inhibiting drugs.

Transported enzymes in sciatic nerve and sensory ganglia of rats exposed to maternal antibodies against nerve growth factor

The accumulations by axoplasmic transport of selected enzyme activities proximal and distal to a ligature placed on the sciatic nerve were monitored in rats exposed in utero to maternal antibodies to nerve growth factor (NGF) and in control rats. Littermates of the animals exposed to anti-NGF were shown elsewhere to have had a 70% reduction in the number of sensory neurons in dorsal root ganglia and a 90% reduction in number of neurons in superior cervical (sympathetic) ganglion. The accumulation of F(-)-sensitive acid phosphatase activity was depressed 75% both proximal and distal to the tie. Accumulation of F(-)-resistant acid phosphatase activity was depressed nearly 50% proximal to the tie. Distal accumulation of this activity did not occur in either group of rats. Accumulation of acetylcholinesterase activity was depressed 30%. Distal accumulation of the activities of beta-glucuronidase and hexokinase was depressed 50%. In the lumbar dorsal root ganglia, dry weight was reduced 40%, and the activities of peroxide-sensitive, F(-)-resistant acid phosphatase and of the mitochondrial enzymes hexokinase, glutamic dehydrogenase, glutamic-oxalacetic transaminase, and NAD-dependent isocitric dehydrogenase were all reduced a little more, 45--50% per ganglion. However, the activities of the lysosomal enzymes, F(-)-sensitive acid phosphatase and beta-glucuronidase, of the peroxide-resistant, F(-)-resistant acid phosphatase, and of the mitochondrial enzyme glutaminase were all reduced about 60% per ganglion. The results of these measurements were interpreted to suggest that much, and perhaps all, of the F(-)-sensitive acid phosphatase activity in motion in peripheral nerve in rat is confined to sensory axons.