Axonal transport of noradrenaline, protein and glycoprotein in cat hypogastric nerves in vitro under conditions of high extracellular glucose.

Abstract

Inferior mesenteric ganglia with attached hypogastric nerves were removed from anaesthetised cats and maintained in Eagle's Minimal Essential Medium in specially designed organ culture chambers for 48 h at 37 degrees C. The chambers had removable barriers so that the fluid bathing the ganglia was separated from that bathing the nerve trunks by inert silicone grease seals. (3H)-fucose (1.25 muCi/ml) and (14C)-leucine (0.5 muCi/ml) were added to the fluid bathing the ganglia at the start of the experiment. At this time, tight ligatures were applied to the hypogastric nerves so that the incorporated isotopes accumulated proximal to the constrictions due to interrupted axonal transport. The nerve trunks were bathed in medium containing glucose at either 5.5 or 25 mmol/l. At the end of the incubation period, the accumulations, proximal to the constrictions, of incorporated leucine and fucose and of noradrenaline were measured. The high glucose medium caused a 27.5% (p less than 0.001) reduction in the accumulation of fucose and a 19.2% (p less than 0.01) reduction in the accumulation of leucine. The incorporation of these tracers in the ganglia was unaffected by exposure of the nerve trunks to high glucose. The accumulation of noradrenaline proximal to the constrictions was also unaffected. Further experiments were performed to show that the reduced accumulations of fucose and leucine under conditions of high glucose were not due to loss of isotope from macromolecules in the axons nor to the small increase in osmotic pressure effected by addition of extra glucose to the culture medium. It is therefore suggested that elevation of extracellular glucose caused an impairment of axonal transport of incorporated leucine and fucose.