Vitros 950

Total serum levels of albumin, glycemia, creatinine, and urea were measured using the dry chemistry method (Ortho-Clinical Diagnostics VITROS 950®, Johnson & Johnson, Rochester, NY) (34 (link)). Total cholesterol (TC), high-density lipoprotein, and triglycerides (TG) were measured by enzymatic colorimetric assay (Ortho-Clinical Diagnostics VITROS 950®, Johnson & Johnson, Rochester, NY). LDL cholesterol was calculated using the Friedewald formula (34 (link)). Fasting insulin levels were measured using a chemiluminescence immunoassay. The homeostasis model of assessment of insulin resistance (HOMA-IR) was calculated with the following formula: [fasting glucose (mmol/L) ^* fasting insulin (μU/mL)/22.5] (34 (link)).

Before euthanasia, 6–8 ml of blood was collected into a heparinized tube for determination of plasma electrolytes and osmolality. For clearance studies, urine samples were immediately stored at -20°C. Plasma concentrations of sodium and potassium were determined on the last day of experiment (Vitros 950, Johnson & Johnson). The concentrations of urinary sodium and potassium were determined by standard flame photometry (Eppendorf FCM6341). The urine and plasma osmolality was measured with a vapor pressure osmometer (Osmomat 030, Gonotec, Berlin, Germany). From the obtained measurements, electrolyte free water reabsorption (T^ecH₂O) was calculated as:
${\mathrm{T}}^{\mathrm{e}}{\mathrm{cH}}_2\mathrm{O}=\mathrm{U}\mathrm{O}\cdot \left(\frac{\mathrm{U}\mathrm{N}\mathrm{a}+\mathrm{U}\mathrm{K}}{\mathrm{P}\mathrm{N}\mathrm{a}}-1\right)$
Where T^ecH₂O is electrolyte free water reabsorption, UO is daily urinary flow rate, UNa is urine sodium, UK is urine potassium, and PNa is plasma sodium [23 (link)–25 (link)].

Total serum levels of C-reactive protein (CRP), albumin, sodium, potassium, creatinine and urea were measured using the dry chemistry method (Ortho-Clinical Diagnostics VITROS 950®, Johnson&Johnson). The hemogram was performed with a Coulter STKS hematological autoanalyzer.