[Mastocytes of the parietal pericardium in the guinea pig].

The present research was performed in the parietal pericardium of guinea pigs aged between 4 and 5 months. After stretching the pericardium on a slide and fixation in Mota's fluid, the following techniques were utilized to study the distribution and the cytochemical characteristics of mastocytes: 1) staining with Toluidine blue or Methylene blue 0,5%; 2) staining with Toluidine blue 10(-4)M in buffered solution at different pH (2,3,4,5,6,7); 3) staining with Alcian blue 8GS pH 1 and pH 2,6. Prior to 1,2,3 a digestion with Ch-ase ABC was performed. The pericardium was also exposed to ortophtaldialdehyde and paraformaldehyde vapours to show the presence of histamine and 5-HT. From our data it results that mastocytes of the parietal pericardium of guinea pig always show an extremely elongated shape. Their granular content is characterized by the presence of condroitinsulphate and ialuronic acid. By the OPT reaction a blue fluorescence becomes evident, showing low histamine levels in mastocytes, while the paraformaldehyde reaction results to be always negative.