By correlating LM and TEM findings with those obtained by HRSEM using a variety of maceration methods, we have previously revealed the 3-D cyto-architecture of human salivary glands acinar and ductal cells. Furthermore, in recent years, in order to study the action of secretagogue drugs at the cellular level, we have devised a technique of in vitro incubation of slices of human salivary glands biopsies. Samples, incubated in a inorganic medium added with drugs acting on specific receptors, were then subjected to our variant (Riva et al., 1999) of the original osmium maceration method by Tanaka and Matsushima (1984) that, following removal of all cytoplasmic organelles, exposes the inner surface of the apical plasmalemma involved in the process of exo-endocytosis, thus allowing, by HRSEM, the visualisation of the drugs effects on an area much larger than that envisioned by TEM. The evaluation of the secretory process was achieved by counting, by statistical methods, the microvilli (mv) and the microbuds (mb, pits) present on 1μm2 of surface area involved in exo-endocytosis. Results demonstrate that our model does give information, otherwise not available in humans, on secretion as shown by the differences seen in the secretory response of serous cells of parotid gland compared with that of serous cells of submandibular. It proved its usefulness also in evaluating the action of drugs that increase or reduce salivation in humans. To elucidate the latter aspect, we have studied the effects of clozapine, the drug of choice for the treatment of certain forms of schizophrenia, that induces, inter alia, severe hypersalivation and drooling, particularly at nightime. Interestingly, our conclusions on the agonist¬/¬antagonist action of the drug have been, for the most, confirmed by experimental studies carried out, in cooperation with us, by Ekström and Godoy (2010) of the University of Goteborg who have performed on rats, a study on the effect of intravenously administered clozapine, and of its active metabolite norclozapine. Our latest investigations have been performed on the secretory effects of pentagastrin (Pg) and of melatonin (Mt), two hormones acting on the GI tract. Again, our findings are in agreement with those obtained experimentally in rat salivary gland by Ekström et al (2006), who demonstrated that with both hormones there is a protein secretion with little fluid. From our results it also appears that whereas Mt acts mainly via exocytosis of secretory granules, Pg seems to cause an higher number of microbuds possibly indicative of a process of vesicle mediated microexocytosis.
Human salivary glands: from electron microscopy (TEM and HRSEM) to pharmacology
LOY, FRANCESCO;Isola R.
2012-01-01
Abstract
By correlating LM and TEM findings with those obtained by HRSEM using a variety of maceration methods, we have previously revealed the 3-D cyto-architecture of human salivary glands acinar and ductal cells. Furthermore, in recent years, in order to study the action of secretagogue drugs at the cellular level, we have devised a technique of in vitro incubation of slices of human salivary glands biopsies. Samples, incubated in a inorganic medium added with drugs acting on specific receptors, were then subjected to our variant (Riva et al., 1999) of the original osmium maceration method by Tanaka and Matsushima (1984) that, following removal of all cytoplasmic organelles, exposes the inner surface of the apical plasmalemma involved in the process of exo-endocytosis, thus allowing, by HRSEM, the visualisation of the drugs effects on an area much larger than that envisioned by TEM. The evaluation of the secretory process was achieved by counting, by statistical methods, the microvilli (mv) and the microbuds (mb, pits) present on 1μm2 of surface area involved in exo-endocytosis. Results demonstrate that our model does give information, otherwise not available in humans, on secretion as shown by the differences seen in the secretory response of serous cells of parotid gland compared with that of serous cells of submandibular. It proved its usefulness also in evaluating the action of drugs that increase or reduce salivation in humans. To elucidate the latter aspect, we have studied the effects of clozapine, the drug of choice for the treatment of certain forms of schizophrenia, that induces, inter alia, severe hypersalivation and drooling, particularly at nightime. Interestingly, our conclusions on the agonist¬/¬antagonist action of the drug have been, for the most, confirmed by experimental studies carried out, in cooperation with us, by Ekström and Godoy (2010) of the University of Goteborg who have performed on rats, a study on the effect of intravenously administered clozapine, and of its active metabolite norclozapine. Our latest investigations have been performed on the secretory effects of pentagastrin (Pg) and of melatonin (Mt), two hormones acting on the GI tract. Again, our findings are in agreement with those obtained experimentally in rat salivary gland by Ekström et al (2006), who demonstrated that with both hormones there is a protein secretion with little fluid. From our results it also appears that whereas Mt acts mainly via exocytosis of secretory granules, Pg seems to cause an higher number of microbuds possibly indicative of a process of vesicle mediated microexocytosis.
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