Secretory effects of pentagastrin and melatonin on human parotid gland in vitro. An HRSEM study

RIVA A;LOY, FRANCESCO;DIANA M;ISOLA R;LANTINI MS;EKSTRÖM J.

2010-01-01

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Abstract

Salivary secretion occurs by multiple pathways which seems to be controlled not only by the autonomic nervous system. In fact, a few works by Aras & Ekström (2006; 2008) have demonstrate, in rat parotid glands, that gastrin-analogue pentagastrin (Pg) and melatonin (Mt) cause protein and amylase- but no fluid secretion. Aim of this work is to quantify, in human salivary serous cells, the morphological changes due to the treatment in vitro with these two hormones. Results will be compared with findings obtained following in vitro stimulation by adrenergic and cholinergic drugs. Methods Human normal parotid fragments were incubated in an inorganic medium added with Mt or Pg and with their inhibitors. Specimens also were incubated in the same medium without the drugs. Samples were processed for high resolution scanning electron microscopy (HRSEM) according to Testa Riva et al. (2006). Results and Conclusions By light microscopy and HRSEM, serous acini treated with the two hormones show typical sign of secretion: a few dilated intercellular canaliculi and profiles of exocytosis, confirming their secretagogue activity. Moreover, a morphometrical analysis, conducted on HRSEM images of the citoplasmic side of intercellular canaliculi, reveals, after each treatment, a decrease of microvilli density, and an increase of microbuds and protrusions density. From our data it results that Mt induce protein secretion principally via exocytosis of secretory granules, while Pg seems to produce an higher number of microbuds possibly indicative of a process of microexocytosis.