Rapamycin induced ultrastructural and molecular alterations in glomerular podocytes in healthy mice

Nephrol Dial Transplant. 2012 Aug;27(8):3141-8. doi: 10.1093/ndt/gfr791. Epub 2012 Jan 30.


Background: In the normal kidney, rapamycin is considered to be non-nephrotoxic. In the present study, we investigated whether rapamycin is indeed non-nephrotoxic by examining the ultrastructural and molecular alterations of podocytes in healthy mice.

Methods: Balb/c mice were given three different intraperitoneal doses of rapamycin for 1 week (dose model)-low-dose group: 1 mg/kg/day, intermediate-dose (ID) group: 1.5 mg/kg/day and high-dose (HD) group: 3 mg/kg/day; four mice in each group. An ID of rapamycin was also given for three different periods (time model): 1, 4 and 8 weeks; four mice were in each group. Mice treated with dimethyl sulphoxide served as controls. Body weight was measured weekly. Renal function was assessed by serum creatinine at the time of sacrifice. For estimation of albuminuria, 24-h urine collections were performed before treatment and weekly thereafter. Glomerular content of nephrin, podocin, Akt and Ser473-phospho-Akt was estimated by western blot and immunofluorescence. Nephrin and podocin messenger RNA (mRNA) were measured by real-time polymerase chain reaction. Mean podocyte foot process width (FPW) was measured by electron microscopy.

Results: Urine albumin levels increased in the HD and 4-week groups. Renal function was modestly deteriorated in the HD group. The mean FPW increased in a dose-dependant manner at Week 1, further deteriorated at Week 4 and finally improved at Week 8. Nephrin and podocin mRNA levels showed a significant decrease at Week 1 and were restored at Week 4 and 8. Nephrin and podocin protein levels were reduced at Week 4 and recovered at Week 8. Ser473-phospho-Akt significantly increased in all rapamycin-treated groups.

Conclusions: Rapamycin induced significant ultrastructural and molecular alterations in podocytes in association with albuminuria. These alterations happened early during treatment and they tended to improve over an 8-week treatment period.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Creatinine / blood
  • Enzyme Activation / drug effects
  • Female
  • Gene Expression / drug effects
  • Immunosuppressive Agents / administration & dosage
  • Immunosuppressive Agents / toxicity
  • Intracellular Signaling Peptides and Proteins / genetics
  • Kidney Transplantation
  • Membrane Proteins / genetics
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Electron, Transmission
  • Podocytes / drug effects*
  • Podocytes / metabolism
  • Podocytes / ultrastructure
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Sirolimus / administration & dosage
  • Sirolimus / toxicity*


  • Immunosuppressive Agents
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • NPHS2 protein
  • RNA, Messenger
  • nephrin
  • Creatinine
  • Proto-Oncogene Proteins c-akt
  • Sirolimus