Histochemical observations on uptake of L-dopa into endocrine cells of the rat pituitary gland during the postnatal development.
The uptake of L-dopa into the cells of the adenohypophysis of the rat was studied during the postnatal development and at adult age using the formaldehyde-induced fluorescence method (FIF). The cells taking up L-dopa were classified by Alcian blue-PAS-Orange G staining. The correlation between the cells taking up L-dopa and those containing tryptophyl-peptide was estimated during the postnatal period and in adult rats. The cells containing tryptophyl-peptide were demonstrated using fluorescence induced by treatment with combined formaldehyde and acetyl chloride vapour. The following observations were made: 1) Great majority of the cells taking up L-dopa did not contain tryptophyl-peptide. Thus the accumulation of L-dopa into the cells of pars distalis is not due to accumulation of L-dopa into the cells by the same transport mechanism as the amino acids for tryptophyl-peptide. 2) Of the cells taking up L-dopa in the adult rats 96% were chromophobes, 2.0% acidophilic cells (somatotrophs and cells producing prolactin), 0.9% R-mucoid cells (corticotrophs), and 1.2% S1- and S2-mucoid cells (gonadotrophs and thyrotrophs). At 10 and 25 days' age the relative numbers of the cells taking up L-dopa were about the same. 3) Pretreatment with nialamide caused only a slight increase in the number of the cells taking up L-dopa. The decrease in the number of the cells uptaking L-dopa of the pars distalis, which takes place after 5 weeks' age is thus not caused by the increased MAO-activity. 4) Strongly chromophilic cells did not take up L-dopa. At the light of our results it seems evident that L-dopa is taken up by the chromophobic cells when these differentiate into chromophilic cells. The accumulation of L-dopa may be a sign of an active transport of amino acids into the cells. The accumulation of L-dopa into the chromophobic stellate and follicular cells may reflect their metabolic activity. These cells probably have an important role in the production of the hormones of the pars distalis.
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D005260:Female; D005453:Fluorescence; D005557:Formaldehyde; D013006:Growth Hormone / Q000378:metabolism; D006651:Histocytochemistry; D007980:Levodopa / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism
D010455:Peptides; D005557:Formaldehyde; D012701:Serotonin; D007980:Levodopa; D014364:Tryptophan; D000324:Adrenocorticotropic Hormone; D013006:Growth Hormone