Endothelin-1 stimulates prostaglandin E2 production in an extracellular calcium-independent manner in cultured rat mesangial cells.
To study a possible role of endothelin-1 (ET-1) in the regulation of glomerular function, we examined the presence of receptors for, and the biological action of, ET-1 in cultured rat mesangial (M) cells. The first-subcultured M cells prepared from isolated glomeruli of Sprague-Dawley rats were used. ET-1 binding was assayed by using 125I-ET-1. Inositol 1,4,5-trisphosphate (IP3) was determined by IP3-specific binding assay. Intracellular calcium (iCa2+) was measured in fura-2 loaded cells. Prostaglandin E2 (PGE2) was measured by radioimmunoassay. In M cells there existed two classes of binding sites specific for ET-1 (Kd was 0.24 and 4.4 nmol/L, Bmax was 130 and 1070 fmol/mg, respectively). ET-1 (10(-7) mol/L) induced a rapid and transient increase in IP3, followed by transient and sustained increases in iCa2+. Nicardipine (10(-6) mol/L) inhibited only the sustained increase in iCa2+. ET-1 (10(-9) mol/L to 10(-7) mol/L) significantly stimulated PGE2 production with the concentration dependency. Nicardipine (10(-6) mol/L) and diltiazem (10(-6) mol/L) did not inhibit the PGE2 production. We conclude that M cells have specific ET-1 receptors linked to phosphoinositide turnover and PGE2 production, and PGE2 production by ET-1 may be through an extra-cellular calcium-independent mechanism. Our results suggest that ET-1 plays an important role in the regulation of glomerular functions by modulating PGE2 production in M cells.
Fukunaga
M
M
First Department of Internal Medicine, Osaka University Medical School, Japan.
Ochi
S
S
Takama
T
T
Yokoyama
K
K
Fujiwara
Y
Y
Orita
Y
Y
Kamada
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D004110:Diltiazem / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000378:metabolism / Q000494:pharmacology*; D016257:Fura-2; D005920:Glomerular Mesangium / Q000166:cytology* / Q000378:metabolism; D006439:Hemodynamics / Q000502:physiology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male; D009529:Nicardipine / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism; D017466:Receptors, Endothelin
D016232:Endothelins; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin; D015544:Inositol 1,4,5-Trisphosphate; D009529:Nicardipine; D004110:Diltiazem; D015232:Dinoprostone; D002118:Calcium; D016257:Fura-2