Endothelium, Vascular/drug effects; Erythropoietin/analogs & derivatives; Erythropoietin/therapeutic use; Multiple Organ Failure/prevention & control; Protein Serine-Threonine Kinases/metabolism; Proto-Oncogene Proteins/metabolism; Animals; Apoptosis/drug effects; Darbepoetin alfa; Disease Models, Animal; Disease Progression; Drug Evaluation, Preclinical; Endothelium, Vascular/enzymology; Endothelium, Vascular/physiopathology; Erythropoietin/administration & dosage; Erythropoietin/pharmacology; Glomerulosclerosis, Focal Segmental/complications; Glomerulosclerosis, Focal Segmental/drug therapy; Glomerulosclerosis, Focal Segmental/pathology; Hematocrit; Hematopoietic Stem Cell Mobilization; Hypertension, Renal/etiology; Hypertension, Renal/physiopathology; Ischemia/prevention & control; Kidney/blood supply; Life Tables; Male; Multiple Organ Failure/etiology; Nephrectomy; Nephritis, Interstitial/etiology; Nephritis, Interstitial/pathology; Proto-Oncogene Proteins c-akt; Random Allocation; Rats; Rats, Sprague-Dawley; Signal Transduction/drug effects