Acid phosphatase in rat neurohypophyseal dispersions and its fractions enriched for neurosecretosomes and pituicytes after water deprivation and lactation.

Neurohypophyseal dispersions and fractions enriched for neurosecretosomes and pituicytes were prepared from rats subjected to 6 days of water deprivation and 9-10 days of lactation as stimuli of the hypothalamo-neurohypophyseal system (HNS). After water deprivation the content of the fractions changed in such a way that the neurosecretosomes, and to a lesser extent also the pituicytes, accumulated at a lower density within the gradient used for separation. Stimulation by means of lactation did not show such changes when a comparison was made with dioestrus. Microchemical and histochemical tests for acid phosphatase showed that most of the activity in the controls was present in the neurosecretosomes. A rough calculation, which takes into account the different yields for the dispersion elements, showed a rather equal distribution for acid phosphatase activity between axonal and pituicytic compartments of the intact neurohypophysis. The known acid phosphatase activity response of the neural lobe after HNS stimulation, which was also detectable in the dispersion, resulted histochemically in an increased staining intensity for both neurosecretosomes and pituicytes, but with microassay it was distributed along a gradient similar to oxytocin. It was therefore concluded that this lysosomal enzyme response within the neurophypophysis is preferentially localized in the neurohypophysis is preferentially localized in the neurosecretory axons.