Angiotensin II requires PDGF-BB to induce DNA synthesis in rat mesangial cells cultured in an exogenous insulin-free medium.
BACKGROUND
Mesangial cell proliferation is an important feature of chronic glomerular disease. Different cytokines and vasoactive substances have been implicated in mesangial cell proliferation. However, the role of angiotensin II remains controversial. Furthermore, all the studies made to date have been performed using a medium supplemented with high concentrations of insulin (5 micrograms/ml) in order to facilitate mesangial cell proliferation in vitro. As has recently been reported, insulin causes a change both in extracellular matrix composition and in mesangial cell phenotype, thus mimicking disease conditions.


METHODS
We examined the effects of Ang II in synchronized and proliferating mesangial cells with and without growth factor (PDGF-BB, bFGF and/or insulin) supplementation and the effects of exogenous administration of insulin on mesangial proliferation by measuring the bromodeoxyuridine (BrdU) uptake.


RESULTS
Angiotensin II itself caused no increase in BrdU incorporation. However, it exerted a significant synergistic effect on PDGF-BB-induced DNA synthesis (P < 0.05) in quiescent medium and tended to stimulate BrdU uptake by proliferating cells (P = 0.09). BrdU incorporation significantly correlated with direct cell count (r = 0.95). PDGF-BB had the maximal stimulatory effect on DNA synthesis both in quiescent and in proliferative culture conditions. The insulin dose (5 micrograms/ml) which has been shown to cause mesangial cell proliferation in vitro, caused an increase in BrdU incorporation by itself in quiescent medium.


CONCLUSIONS
We conclude that in an insulin-free medium, mimicking in vivo glomerular conditions, PDGF-BB or proliferative medium are needed to allow Ang II-induced DNA synthesis in mesangial cell culture.
Higueruelo
S
S
Nephrology Unit, Hospital Universitario Germans Trias i Pujol, Badalona, Spain.
Romero
R
R
D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D000077214:Becaplermin; D001713:Biphenyl Compounds / Q000008:administration & dosage / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media; D004247:DNA / Q000096:biosynthesis*; D004357:Drug Synergism; D016222:Fibroblast Growth Factor 2 / Q000008:administration & dosage / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D005921:Glomerulonephritis / Q000209:etiology; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D019808:Losartan; D010982:Platelet-Derived Growth Factor / Q000008:administration & dosage / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D013777:Tetrazoles / Q000008:administration & dosage / Q000494:pharmacology
D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D003470:Culture Media; D007093:Imidazoles; D007328:Insulin; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D013777:Tetrazoles; D016222:Fibroblast Growth Factor 2; D000804:Angiotensin II; D000077214:Becaplermin; D004247:DNA; D019808:Losartan