Electron microscopic histochemistry of cholinesterase in the posterior, intermediate, and anterior lobes of the rat pituitary

Butyrylcholinesterase activity in the developing auditory brainstem, the choroid plexus and the pituitary of the perinatal rat

The butyrylcholinesterase activity in the vasculature of the brain, choroid plexus, and pituitary, was studied histochemically in rats during postnatal days 1, 7, 14, 21 and 28. The brainstem auditory nuclei were used for comparison of vessels at different ages. We found intense butyrylcholinesterase activity in all intraparenchymal blood vessels, especially capillaries, in all ages. In the meningeal vessels, activity was especially prominent in 1 and 7 day old animals when the perineural meninges was relatively thick. In the pituitary, reaction for the enzyme was found in nonvascular elements, especially in the intermediate and posterior lobes. Vessels of the choroid plexus were associated with punctate regions of butyrylcholinesterase activity. These results do not support the suggestion of a major role for butyrylcholinesterase in the blood-brain barrier.

Localization of acetylcholinesterase and choline acetyltransferase in the rat pituitary gland

Experiments were conducted to determine the presence of two cholinergic biomarkers, acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) in the rat pituitary. A histochemical procedure for AChE was used to provide visualization of structures containing this enzyme. Radiochemical methods provided a sensitive assay for measuring ChAT activity. Nerve fibres staining for AChE activity were observed in the neurointermediate lobe, with the greatest concentrations appearing at the junction region with the pituitary stalk. Cells staining for AChE were found in the pars distalis and pars intermedia. ChAT activity correlated well with AChE distribution in pars nervosa and pars intermedia but not in pars distalis. The greatest levels of ChAT activity were in pars intermedia and the region where the stalk joins the pituitary. Significant values were also found for the pars nervosa. The presence of AChE and ChAT in pars intermedia and pars nervosa is evidence for a cholinergic innervation to these regions. In pars distalis, where other investigators have found muscarinic receptors, intense staining for AChE and absence of ChAT activity may indicate non-innervated, acetylcholine-sensitive sites.

Stimulatory effect of dihydrotestosterone on the acetylcholinesterase activity of rat adenohypophysis

Acetylcholinesterase (AChE) activity in the adenohypophysis of adult orchidectomized rats, and of orchidectomized rats treated with 100 microgram/100 g b.w. of dihydrotestosterone (DHT), was determined by a spectrophotometric method. Our result shows a significant increase in AChE activity of the adenohypophysis of orchidectomized rats treated with DHT.

Observations on the functional cytochemistry of pars intermedia of the rat hypophysis

Light and electron microscopic histochemical reactions were studied in the cells of pars intermedia of the rat. The possible correlations between enzymatic reactions and endocrine functions of these cells were discussed. By combined formaldehyde and chloral vapour treatment the cells of the pars intermedia exhibited a strong yellow fluorescence suggesting the presence of a peptide or peptides with NH2-terminal tryptophan. Masked metachromasia after acid hydrolysis was probably due to these peptides. Only a weak or no alpha-glycerophosphate dehydrogenase and nonspecific esterase activity was observed in the cells of pars intermedia compared to the cells of pars distalis suggesting low production rate of hormone synthesis. Specific and non-specific cholinesterases were demonstrated light and electron microscopically constantly in the cells bordering the lobules. These cells probably represent a certain type of glial cells. In the other cells the enzymatic activities varied markedly in intensity and distribution showing different ultrastructural localizations. Thus cholinesterase activities in the cells of pars intermedia reflect possibly different functional stages of the cells in their hormone production, storage and secretion processes.