title: Pulmonary epithelial clearance of 99mTc-DTPA after thrombin-induced pulmonary microembolism.
abstract: We investigated the effect of thrombin-induced pulmonary microembolism on the pulmonary clearance rate of aerosolized 99mTc diethylenetriamine pentaacetic acid (99mTc-DTPA) in awake, chronically prepared sheep. Chest activity was recorded after administration of a 0.44 micron aerosol of 99mTc-DTPA. Decay-corrected data were fit to an exponential and expressed as percent decrease per min (%/min). Sheep were given alpha-thrombin intravenously (80 U/kg for 10 min) 60 min after the aerosol administration. The clearance rate prior to alpha-thrombin was 0.35 +/- 0.05 %/min (mean +/- SEM). During alpha-thrombin administration, the clearance rate increased to 5.84 +/- 0.70 %/min (p less than 0.001 from baseline), but returned to 0.41 +/- 0.06 %/min within 30 min after the end of the thrombin infusion. The increased clearance rate during alpha-thrombin administration was not due to increased lung volume since alpha-thrombin did not change functional residual capacity. Moreover, the clearance rate was unchanged during gamma-thrombin administration, which does not induce coagulation, or during alpha-thrombin challenge in defibrinogenated animals. alpha-thrombin administration in neutrophil-depleted sheep caused a transient increase in DTPA clearance similar to that in control sheep, suggesting that the increase occurred independently of neutrophils. The results indicate that alpha-thrombin causes a large, transient increase in 99mTc-DTPA clearance, which may be the result of increased epithelial permeability. This response is dependent on the activation of intravascular coagulation.
mesh_terms: D000336:Aerosols; D000818:Animals; D002199:Capillary Permeability; D004848:Epithelium / Q000378:metabolism; D005652:Functional Residual Capacity; D008168:Lung / Q000378:metabolism*; D004369:Pentetic Acid / Q000008:administration & dosage; D011655:Pulmonary Embolism / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D012756:Sheep; D013667:Technetium / Q000008:administration & dosage; D016284:Technetium Tc 99m Pentetate; D013917:Thrombin / Q000008:administration & dosage
chemical_list: D000336:Aerosols; D013667:Technetium; D004369:Pentetic Acid; D013917:Thrombin; D016284:Technetium Tc 99m Pentetate