Intracellular [Ca2+] and inositol phosphates in avian nasal gland cells.
Isolated cells from the nasal salt gland of ducklings (Anas platyrhynchos) were evaluated as a model system for the study of the muscarinic activation of exocrine ion secretion. Cells loaded with the fluorescent probe indo-1 were used to study changes in intracellular Ca2+ concentration [( Ca2+]i) after stimulation. Changes in inositol phosphate generation and oxygen consumption were also determined. Loading with the acetomethoxy ester form of indo-1 (indo-1/AM) was rapid, and intracellular cleavage of the ester was essentially complete. Leakage of the dye was negligible over the time course of measurements (up to 20 min). Resting [Ca2+]i was approximately 100 nM. Stimulation with carbachol resulted in progressive increases in the generation of inositol phosphates and rapid four- to fivefold increases in [Ca2+]i. At normal extracellular Ca2+ concentrations, [Ca2+]i remained elevated (approximately 3 times resting levels) for as long as stimulation continued. Experiments showed that the increases in [Ca2+]i were comprised of a combination of release of Ca2+ from intracellular stores and an enhanced entry of Ca2+ from the extracellular medium. It is specifically this latter process that produces the sustained elevations in [Ca2+]i that are the essential signal for secretory activity.
Shuttleworth
T J
TJ
Department of Physiology, University of Rochester School of Medicine and Dentistry, New York 14642.
Thompson
J L
JL
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival; D004372:Ducks / Q000378:metabolism*; D005088:Exocrine Glands / Q000166:cytology / Q000378:metabolism*; D005456:Fluorescent Dyes; D007211:Indoles; D007295:Inositol Phosphates / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D009296:Nasal Cavity / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D010101:Oxygen Consumption; D010277:Parasympathomimetics / Q000494:pharmacology
D005456:Fluorescent Dyes; D007211:Indoles; D007295:Inositol Phosphates; D010277:Parasympathomimetics; C048960:indo-1; D002118:Calcium