title: Bone extraction and blood clearance of diphosphonate in the dog.
abstract: The transcapillary extraction of diphosphonate, as [99mTc]EHDP, a substance used in bone scanning and for management of certain metabolic bone diseases, has been examined. The maximum instantaneous extraction for [99mTc]EHDP was 0.27 +/- 0.05 (mean +/- SD, N = 10) and the net extraction at 5 min was 0.18 +/- 0.05 (N = 10). The permeability ratio of [99mTc]EHDP to the freely diffusible compound, sucrose, using the formula PS = -Fs loge (1 - Emax), was 0.71. This is similar to the ratio of diffusion coefficients of EHDP to sucrose, which is estimated to be 0.78. These results suggest that the mechanism by which [99mTc]EHDP passes through the capillaries in bone is passive diffusion. Tissue level estimations of EHDP confirm a rapid blood clearance associated with an increase in the rate of urinary excretion; the level of [99mTc]EHDP in bone, however, remains constant. The fractional excretion of [99mTc]EHDP was 27.3 +/- 2.0% in control dogs and was unchanged by thyroparathyroidectomy and subsequent infusion of parathyroid hormone.
mesh_terms: D000818:Animals; D001847:Bone Diseases / Q000175:diagnosis*; D001842:Bone and Bones / Q000098:blood supply; D002196:Capillaries; D002199:Capillary Permeability; D004058:Diffusion; D004285:Dogs; D012968:Etidronic Acid / Q000097:blood / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008297:Male; D008433:Mathematics; D010280:Parathyroid Glands / Q000601:surgery; D010281:Parathyroid Hormone / Q000494:pharmacology; D011877:Radionuclide Imaging; D013326:Strontium Radioisotopes / Q000378:metabolism; D013667:Technetium; D013965:Thyroidectomy
chemical_list: D010281:Parathyroid Hormone; D013326:Strontium Radioisotopes; D013667:Technetium; D012968:Etidronic Acid