Lipid secretory mechanisms in the mammalian harderian gland.
The mammalian Harderian glands are lipid-secreting glands. In an unstimulated condition, the glandular cells frequently exocytose the lipid materials; however, no intracellular calcium ion ([Ca2+]c) changes are detectable. Cholinergic (muscarinic) secretagogues induce secretory activity and increase of [Ca2+]c. A G-protein activator, sodium fluoride, enhances the secretory activity and increase of [Ca2+]c. Removal of extracellular calcium ions inhibits the secretion enhanced by cholinergic stimulation. Under pharmacologic stimulation, glandular cells may show an apocrine-like secretory pattern. Cholinergic stimulation also induces contraction of the myoepithelial cells covering glandular end pieces; however, the reduction in volume of glandular end pieces is not prominent. Catecholamines have no effect on the release of lipid materials. These results indicate the involvement of G-proteins linking with muscarinic receptors and Ca2+ dynamics (increase of [Ca2+]c and Ca2+ influx) in lipid secretion by glandular cells and in contraction of myoepithelial cells of mammalian Harderian glands. However, the increase of [Ca2+]c in Harderian glands was less when compared with other cells--for instance, those which secrete protein.
Satoh
Y
Y
Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
Gesase
A P
AP
Habara
Y
Y
Ono
K
K
Kanno
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D006224:Cricetinae; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D005089:Exocytosis; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology; D006168:Guinea Pigs; D006243:Harderian Gland / Q000378:metabolism* / Q000648:ultrastructure; D050356:Lipid Metabolism; D051379:Mice; D018721:Muscarinic Agonists / Q000378:metabolism; D051381:Rats; D012969:Sodium Fluoride / Q000378:metabolism
D002395:Catecholamines; D018721:Muscarinic Agonists; D012969:Sodium Fluoride; D019204:GTP-Binding Proteins; D002118:Calcium