Sphingosine stimulates calcium mobilization in rat parotid acinar cells.
In fura-2-loaded parotid acinar cells, 50-200 microM sphingosine induced an increase in cytosolic Ca2+ ([Ca2+]i). When extracellular Ca2+ was chelated by EGTA, 50 microM sphingosine failed to increase [Ca2+]i, but 100 or 200 microM sphingosine induced a slight and transient increase in [Ca2+]i. The addition of LaCl3 to the medium resulted in the same effect as chelation of extracellular Ca2+. When cells were incubated in low Ca2+ medium containing sphingosine, and extracellular Ca2+ was subsequently added, a rapid increase in [Ca2+]i depending on the concentration of sphingosine was shown. In low Ca2+ medium, a slight increase in [Ca2+]i induced by high concentrations of sphingosine was not shown after the transient increase in [Ca2+]i elicited by methacholine. Inhibitors of protein kinase C, H-7 and K252a, did not mimic the effect of sphingosine on [Ca2+]i. These results suggest that sphingosine stimulates Ca(2+)-influx and further stimulates the release of Ca2+ from agonist-sensitive intracellular pools by a mechanism that is independent of protein kinase C.
Sugiya
H
H
Department of Physiology, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
Furuyama
S
S
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D016257:Fura-2 / Q000378:metabolism; D008297:Male; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013110:Sphingosine / Q000494:pharmacology*
D011493:Protein Kinase C; D013110:Sphingosine; D002118:Calcium; D016257:Fura-2