Pattern of prepro-endothelin-1 expression revealed by reporter-gene activity in kidneys of erythropoietin-overexpressing mice.
Transgenic overexpression of erythropoietin (Epo) in mice increases haematocrit to a mean of 80% in adult mice, leading to an increase in blood viscosity and volume. As a consequence, renal tissue endothelin-1 (ET-1) concentrations are significantly elevated in erythropoietin-overexpressing (Epo+) mice (mean+/-S.E.M; Epo+, 798+/-71; Epo-, 400+/-25 pg/g tissue; P<0.01). To investigate the pattern of expression of the primary translation product of the ET-1 gene, prepro-ET-1, in kidneys of (Epo+) mice, we generated crossbred mice overexpressing the human EPO gene with mice carrying a reporter gene construct expressing the LacZ gene under the control of the human prepro-ET-1 promotor sequence (LacZ+/Epo+). For comparison, we generated (LacZ+/Epo-) mice from the same strains. After Bluo-Gal staining of frozen kidney sections (n=10 in each group), intracellular blue precipitates as indicators of prepro-ET-1 promotor activity were detectable in tubular and vascular endothelium and glomerular cells in (LacZ+/Epo-) as well as (LacZ+/Epo+) mice. Comparison of the amount of blue precipitates by semiquantitative scoring showed a significant increase in reporter gene activity in tubular epithelium of (LacZ+/Epo+) mice (mean+/-S.E.M.; LacZ+/Epo+, 1.64+/-0.18; LacZ+/Epo-, 1.00+/-0.19; P<0.05). Reporter gene activity was not significantly elevated in epithelium of small intrarenal arteries of (LacZ+/Epo+) mice (mean+/-S.E.M.; LacZ+/Epo+, 0.86+/-0.14; LacZ+/Epo-, 0.38+/-0.21; P=0.08) and was similar in glomerular cells (mean+/-S.E.M.; LacZ+/Epo+, 1.28+/-0.16; LacZ+/Epo-, 1.14+/-0.21; P=0.6). The main source of elevated ET-1 tissue concentration in kidneys of (Epo+) mice therefore seems more likely to be tubular than vascular endothelium or glomerular cells.
Department of Nephrology, University Hospital Charité, Humboldt University of Berlin, D-10117 Berlin, Germany.
Torsten
T
Slowinski
Norma
N
Schulz
Frank T
FT
Ruschitzka
Thomas
T
Quaschning
Christian
C
Bauer
Franz
F
Theuring
Hans-H
HH
Neumayer
Max
M
Gassmann
Berthold
B
Hocher
D000818:Animals; D001947:Breeding; D019332:Endothelin-1 / Q000032:analysis; D016232:Endothelins / Q000235:genetics*; D004921:Erythropoietin / Q000235:genetics*; D015870:Gene Expression; D017930:Genes, Reporter; D007668:Kidney / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D011498:Protein Precursors / Q000235:genetics*; D001616:beta-Galactosidase / Q000235:genetics
D019332:Endothelin-1; D016232:Endothelins; D011498:Protein Precursors; D004921:Erythropoietin; D001616:beta-Galactosidase