Expression of an allozyme of prorenin-converting enzyme in the submandibular gland of DBA/2N mice

Endoplasmic reticulum stress affects mouse salivary protein secretion induced by chronic administration of an α1-adrenergic agonist

Stress stimulates both the sympathetic-adrenomedullary and hypothalamus-pituitary-adrenal axes. Activation of these axes results in the release of catecholamines, which in turn affects salivary secretion. Thus, repetitive stimulation of the α₁-adrenergic receptor could be useful for studying the effects of chronic stress on the salivary gland. Salivary protein concentration and kallikrein activity were significantly lower in mice following chronic phenylephrine (PHE) administration. Chronic PHE administration led to significantly increased expression of the 78-kDa glucose-regulated protein, activating transcription factor 4, and activating transcription factor 6. Histological analyses revealed a decrease in the size of the serous cell and apical cytoplasm. These results suggest that repetitive pharmacological stimulation of the sympathetic nervous system elicits ER stress and translational suppression. In addition, PHE-treated mice exhibited a decrease in intracellular Ca²⁺ influx elicited by carbachol, a muscarine receptor agonist in the submandibular gland. The present findings suggest that chronic psychological, social, and physical stress could adversely affect Ca²⁺ regulation.

Prorenins activation by an enzyme from rat plasma (PreR-Co)

The aim of the present research was to explore the capacity of PreR-Co to process prorenin purified from kidney and corpora lutea (CL) and to study its action on extrarenal tissues. The PreR-Co was obtained from plasma as a single electrophoretic band by (NH4)2SO4 precipitation, gel filtration, anti-rat albumin immunoaffinity, and ion-exchange chromatography. Prorenin free of renin was obtained after (NH4)2SO4 precipitation, gel filtration, and ion-exchange chromatography by a passage through an affinity gel of H-77 Sepharose. SDS-PAGE of supernatant and of acidic elution from gel, exhibited a single band of 43 kDa and 35 kDa, respectively; both recognized by the specific anti rat renin antibody. The isolated renin was not attacked by PreR-Co; on the contrary prorenin was completely activated. The product of PreR-Co-activated prorenin showed an analogous MW to that of renin and was recognized by the specific antibody. In addition to processing kidney prorenin, PreR-Co was able to cleave inactive renin from ovary, CL, uterus and adrenal gland homogenates. However, the amount of active renin generated from these tissues was lower than those produced by trypsin activation. PreR-Co is a good candidate for the role of the enzyme involved in tissues prorenin activation.

Involvement of vesicle-cytoskeleton interaction in AQP5 trafficking in AQP5-gene-transfected HSG cells

A cDNA of rat aquaporin 5 (AQP5) was used to transfect to HSG (human salivary gland cells), and the trafficking mechanism was studied in vitro by confocal laser microscopy. The trafficking of AQP5 to the plasma membrane was induced by stimulation of AQP5-gene-transfected human salivary gland cells (HSGAQP5 cells) with thapsigargin, an inhibitor of endoplasmic Ca(2+)-ATPase, and or with A-23187, a calcium ionophore. Pretreatment of these cells with colchicine or vinblastine, microtubule inhibitors, prevented the trafficking induced by thapsigargin or A-23187. The trafficking event was not completely inhibited by cytochalasin B, a microfilament inhibitor. These results demonstrate that the trafficking of AQP5 vesicles to the plasma membrane is triggered by an increase in intracellular Ca(2+) and that the interaction of AQP5-containing vesicles with the cytoskeleton is involved in this trafficking.