Formaldehyde-ozone-induced fluorescence in pituitary ACTH cells: effect of adrenalectomy

Fluorescence histochemical methods for the study of peptide hormone-producing cells

Fluorescence histochemical methods for the demonstration of specific residues in peptides and proteins are reviewed: Formaldehyde-ozone for NH2-terminal tryptophan, formaldehyde-HCl for tryptophan regardless of position in the peptide, OPT for NH2-terminal histidine, formaldehyde-fluorescamine for "protected" amino groups, nitroso-naphthol for tyrosine, and phenanthrenequinone for arginine residues. The methods are potent in demonstrating granule-stored material in peptide hormone-producing cells. Also quinacrine, the fluorescent anti-malaria agent, binds to granular components, as yet unidentified, in several endocrine cell types. In many cases the fluorescence histochemical methods seem to demonstrate peptides and proteins distinct from the known hormones.

Tryptophylglycine dipeptide in ACTH/MSH cells of the human hypophysis: its identification and studies on its antinociceptive effects in mice

The ACTH/MSH cells of the pars distalis and pars intermedia of the mammalian hypophysis contain peptides with amino-terminal tryptophan which exhibit a strong fluorescence after treatment with modified formaldehyde vapour methods and with glyoxylic acid in the tissue sections from freeze-dried specimens. By homogenization of the hypophyses in ethanolic glyoxylic acid and subsequent heating the peptides can be converted to highly fluorescent beta-carboline derivatives; these can then be extracted with glacial acetic acid, separated by silica gel thin-layer chromatography and identified in UV light. Amino-terminal tryptophyl peptide from adult human hypophysis extracted and treated in this way gave the structure L-tryptophylglycine after acid hydrolysis. This structure was subsequently confirmed by producing a fluorescent derivative from authentic L-tryptophylglycine using the same reaction conditions as for the tissue homogenate. This derivative moved in the same way in thin-layer chromatography as fluorecent amino-terminal tryptophyl peptide extracted from human hypophysis. Thereafter a study was made of the antinociceptive effects of authentic L-tryptophylglycine administered subcutaneously in mice both alone and together with morphine. L-tryptophylglycine had no antinociceptive effects alone and neither did it change morphine antinociception. Also it had no apparent effects on the behaviour of mice. Thus, ACTH/MSH cells contain a dipeptide whose physiological function differs from the effects of ACTH, MSH and endorphins.

Quantitative fluorescence histochemistry of combined formaldehyde-chloral-induced fluorescence of amino-terminal tryptophyl-peptide in model experiments and in the pars intermedia of the rat hypophysis

The relationship between the intensity of combined formaldehyde-chloral vapour-induced fluorescence and the concentration of amino-terminal tryptophyl-peptide in model experiments was found to be non-linear. At a certain concentration the intensity began to increase more slowly than the concentration, and when the concentration further increased the intensity even began to decrease. Based on the studies previously reported and on the above findings it seems that fluorescence induced by combined formaldehyde-chloral vapour, glyoxylic acid vapour and possibly also other combined formaldehyde and carbonyl compounds in the hypophyseal cells containing amino-terminal tryptophyl-peptides is quenched in normal conditions due to the high local concentration. Thus, small to moderate changes in the amounts of amino-terminal tryptophyl-peptides cannot be observed by measuring the fluorescence intensity. In tissue experiments the intensity of combined formaldehyde-chloral vapour-induced fluorescence in the rat pars intermedia was measured after reserpine treatment, which decreases the number of hormone storage granules as demonstrated electron microscopically. The fluorescence intensity measurements were combined with an estimation of the amounts of amino-terminal tryptophyl-peptides extracted from hypophyses and separated in thin-layer chromatography, and subsequently demonstrated by combined formaldehyde-chloral vapour and a protein stain (amido black). Reserpine treatment decreased the fluorescence intensity in the pars intermedia and in thin-layer chromatography, and the staining of the fluorescent band with amido black was also decreased. Amino-terminal tryptophyl-peptides appeared to be depleted from the pars intermedia cells together with endorphins and other hormones of the ACTH/MSH cells containing tryptophan.