Effects of parathyroid hormone depletion in dogs with induced renal failure

Six parathyroidectomized (PTX) and 6 control dogs had renal mass reduced by 15/16, and were studied for effects of parathyroid hormone depletion on progression of renal failure. All PTX dogs and 4 of 6 control dogs survived until necropsy after 32 weeks. Plasma parathyroid hormone concentration was undetectable in PTX dogs throughout the study, but was greater than normal in control dogs. Serum inorganic phosphate (P) concentration was increased in PTX dogs (6.8 +/- 0.1 mg/dl) and in control dogs (7.5 +/- 0.2), but did not differ significantly (P = 0.254) between groups. Ionized blood calcium values (Ca2+) were significantly (P = 0.014) lower in PTX dogs (1.31 +/- 0.01 mmol/L) than in control dogs (1.36 +/- 0.00 mmol/L), but were more variable in PTX dogs. Values in PTX dogs were not significantly different from those in control dogs for glomerular filtration rate (P = 0.914), plasma creatinine concentration (P = 0.903), and urine protein to creatinine ratio (P = 0.756) determined at intervals during the study. Terminal glucose tolerance and plasma insulin concentrations, P tolerance, and renal P excretion did not differ between groups. Histologic comparison of kidneys removed during reduction of renal mass with kidneys removed at necropsy revealed development of lesions in both groups of dogs, and no protective effect from parathyroidectomy. Mineral analysis of aorta, brain, heart, lungs, and skeletal muscle obtained at necropsy revealed no significant difference between PTX and control groups. Renal cortical calcium concentration was significantly (P < 0.05) greater in kidneys obtained at necropsy then in kidneys obtained during nephrectomy, but PTX did not protect renal cortex from calcium deposition.