Morphological and functional characterization of the thoracic portion of blowfly salivary glands |
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Authors: | Rotte Cathleen Walz Bernd Baumann Otto |
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Institution: | aInstitut für Biochemie und Biologie, Zoophysiologie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam-Golm, Germany |
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Abstract: | The abdominal portion of the salivary glands in the blowfly has been studied intensively. Here, we examine the thoracic part of the salivary glands, emphasizing structural and functional aspects. The initial segment downstream of the abdominal portion is secretory and resembles the latter in most structural and functional aspects: the apical membrane is enfolded, forms a canalicular system and contains V-H+-ATPase that assembles upon stimulation with the hormone serotonin (5-HT); Na,K-ATPase is localized in the basolateral membrane; septate junctions are not prominent, as deduced from immunofluorescence staining for the marker proteins discs large and fasciclin III. 5-HT elicits, at low concentrations, cytoplasmic Ca2+] oscillations, and, at saturating concentrations, a tonic Ca2+] rise. The following, so-called “re-absorptive” segment loops through the coiled secretory portion of the salivary gland. The apical membrane of the re-absorptive cells is not enfolded, and septate junctions are prominent. V-H+-ATPase and Na,K-ATPase reside on the apical and basolateral membranes, respectively. Finally, re-absorptive cells are also sensitive to 5-HT; however, whereas V-ATPase assembly has a 5-HT concentration dependence similar to other segments, the Ca2+ response occurs only at higher 5-HT concentrations, and displays a different kinetic pattern. |
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Keywords: | Salivary glands Calliphora Insect Ion transport Na K-ATPase Vacuolar H+-ATPase Serotonin Ca2+ oscillations Septate junctions |
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