Identification of high molecular weight neurophysins in extracts of human neurohypophyseal tissue.

Acid extracts of human neurohypophyseal tissue were found to contain neurophysin-immunoreactive proteins in the 17,000-20,000 dalton molecular weight range by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The 17,000-20,000 dalton neurophysins persisted under reducing conditions. Limited chymotrypsin proteolysis of the 17,000-20,000 dalton neurophysins generated both increased 10,000 dalton neurophysin and also 4000-8000 dalton vasopressin immunoreactivity. These 'big' neurophysins appear to represent precursor forms of the neurophysins and the neurohypophyseal hormones, which are present within the neurosecretory granules of the human posterior pituitary.