EFFECT OF HAEMORRHAGE ON THE RAPID AXONAL TRANSPORT OF NEUROHYPOPHYSIAL PROTEINS OF THE RAT

Following injection of [³⁵S]cysteine into the region of the supraoptic nucleus male rats were subjected to haemorrhage and the radioactivity of the supraoptic nucleus and neurohypophysial proteins was measured at various time intervals after injection. Following haemorrhage the incorporation of [³⁵S]cysteine into supraoptic nucleus proteins increased. Evidence was obtained for a lag period of 1 to 2 h for the supraoptic nucleus proteins to become available for axonal transport. As judged from the time of arrival of labelled material in the neurohypophysis, haemorrhage did not change the rapid rate of axonal transport (190 mm/day). At 15 min following bleeding, the radioactivity in fraction A (a neurophysin) of the neurohypophysis was reduced, which indicated a release of this rapidly transported protein. During the following 15 min an increase in the protein-bound radioactivity of the neural lobe occurred which exceeded that in controls. This is taken as evidence for increased axonal transport in response to haemorrhage.