title: Effects of posture on regional pulmonary blood flow in rats as measured by PET.
abstract: Using small animal PET with (68)Ga-radiolabeled human albumin microspheres (Ga-68-microspheres), we investigated the effect of posture on regional pulmonary blood flow (PBF) in normal rats. This in vivo method is noninvasive and quantitative, and it allows for repeated longitudinal measurements. The purpose of the experiment was to quantify spatial differences in PBF in small animals in different postures. Two studies were performed in anesthetized, spontaneously breathing Wistar rats. Study 1 was designed to determine PBF in the prone and supine positions. Ga-68-microspheres were given to five prone and eight supine animals. We found that PBF increased in dorsal regions of supine animals (0.75) more than in prone animals (0.70; P = 0.037), according to a steeper vertical gradient of flow in supine than in prone animals. No differences in spatial heterogeneity were detected. Study 2 was designed to determine the effects of tissue distribution on PBF measurements. Because microspheres remained fixed in the lung, PET was performed on animals in the position in which they received Ga-68-microsphere injections and thereafter in the opposite posture. The distribution of PBF showed a preference for dorsal regions in both positions, but the distribution was dependent on the position during administration of the microspheres. We conclude that PET using Ga-68-microspheres can detect and quantify regional PBF in animals as small as the rat. PBF distributions differed between the prone and supine postures and were influenced by the distribution of lung tissue within the thorax.
authors.affiliation: Department of Anesthesia and Critical Care, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. torsten.richter@uniklinikum-dresden.de
authors.forename: Torsten
authors.initials: T
authors.lastname: Richter
authors.forename: Ralf
authors.initials: R
authors.lastname: Bergmann
authors.forename: Jens
authors.initials: J
authors.lastname: Pietzsch
authors.forename: Inge
authors.initials: I
authors.lastname: Közle
authors.forename: Frank
authors.initials: F
authors.lastname: Hofheinz
authors.forename: Eik
authors.initials: E
authors.lastname: Schiller
authors.forename: Maximilian
authors.initials: M
authors.lastname: Ragaller
authors.forename: Jörg
authors.initials: J
authors.lastname: van den Hoff
mesh_terms: D000818:Animals; D002196:Capillaries / Q000187:drug effects; D005710:Gallium Radioisotopes / Q000008:administration & dosage / Q000493:pharmacokinetics; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology*; D008297:Male; D008863:Microspheres; D049268:Positron-Emission Tomography; D011187:Posture / Q000502:physiology*; D016684:Prone Position / Q000502:physiology; D011652:Pulmonary Circulation / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012984:Software; D016683:Supine Position / Q000502:physiology; D013909:Thorax / Q000000981:diagnostic imaging / Q000502:physiology; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D005710:Gallium Radioisotopes