Subcellular distribution of neurophysin in rats subjected to haemorrhage, salt-loading and lactation and in rats with hereditary diabetes insipidus (Brattleboro strain).

Abstract

The subcellular distribution of radioactive neurophysin and the release of neurophysin from isolated neurosecretory granules (NSG) from the posterior pituitary gland were studied at various time intervals after injection of (35S) cysteine into the supraoptic nucleus under various functional conditions. In consistency with previous findings (Norstrom, 1972), increased amounts of radioactive neurophysin were recovered extra-granularly at longer time intervals after isotope injection. Increased quantities of “free” labelled neurophysin were found in lactating rats and homozygous diabetes insipidus (DI) rats 7 and 1 day after injection, respectively. Salt-loading for 4 days did not affect the subcellular distribution of radioactive neurophysin 1 day after injection of (35S) cysteine. 8.5 days after isotope injection acute haemorrhage was followed by augmented amounts of radioactive neurophysin among the soluble proteins, but at 1 day no difference was observed between bled animals and controls. The “spontaneous” release of neurophysin form NSG was higher in stimulated animals and increased with time after isotope injection in controls as well as in experimental animals. The absolute increase in release of neurophysin in response to ATP was higher in stimulated rats whereas NSG from DI rats did respond poorly to ATP.