Microspheres method for ocular blood flow measurement in rats: size and dose optimization.

This study modified the microspheres method by optimizing the dose and size of microspheres (MS) to enable accurate ocular blood flow measurement in rats. Fluorescent MS, either 6, 8, 10 or 15 microm diameter, were administered into the left ventricle of anesthetized adult Brown Norway rat in a dose of either 10(6), 5x10(6), or 10(7). The total number of MS entrapped in retina, choroid and optic nerve (Ntissue) was quantified and compared between size and dose groups. The MS distribution in the retina and their reentry into systemic circulation were evaluated for different sized MS. The results showed that at the 5x10(6) dose, the Ntissue of 8 microm MS was significantly more than either 6 or 10 microm MS in the retina (P<0.02) and optic nerve (P<0.03). The 10 microm MS produced the highest Ntissue for the choroid, as compared with either 8 or 6 microm MS (P<0.03). At the 10(6) dose, no difference of N(tissue) was found between 8, 10, and 15 microm MS in the retina. The 10 microm MS yielded the highest Ntissue in the choroid as compared to 8 and 15 microm MS (P<0.003). The Ntissue for 8 microm MS was higher than both 10 and 15 microm (P<0.01) MS in the optic nerve. No MS (>or=8 microm) reentered the systemic circulation. The 15 microm MS tended to lodge in pre-capillary arterioles and caused significant blood pressure increase during the injection. The blood flow measured with the optimal size MS (mean+/-SE) were 19+/-3.4 and 170+/-35 microl/min in the retina and choroid, respectively; and 0.18+/-0.03 microl/min per mm optic nerve. It is concluded that the 8 microm MS are the optimal size for both retinal and optic nerve blood flow estimation; the 10 microm for the choroid. The optimal dose for the retina was approximately 2.5x10(6), 0.5x10(6) for the choroid, and 5x10(6) approximately 10(7) for the optic nerve. The 15 microm MS are inappropriate for ocular blood flow measurements in rats.

[1]  R. Funk,et al.  Blockers of carbonic anhydrase can cause increase of retinal capillary diameter, decrease of extracellular and increase of intracellular pH in rat retinal organ culture , 2003, Graefe's Archive for Clinical and Experimental Ophthalmology.

[2]  J I Hoffman,et al.  Blood flow measurements with radionuclide-labeled particles. , 1977, Progress in cardiovascular diseases.

[3]  J. R. Ewen,et al.  High spatial resolution measurements of organ blood flow in small laboratory animals. , 2000, American journal of physiology. Heart and circulatory physiology.

[4]  T. Inomata,et al.  Microvasculature of the hamster eye: scanning electron microscopy of vascular corrosion casts. , 2001, Veterinary ophthalmology.

[5]  Y. Nose,et al.  The microsphere method facilitates statistical assessment of regional blood flow , 1985, Basic Research in Cardiology.

[6]  L. Bankir,et al.  THE MEASUREMENT OF GLOMERULAR BLOOD FLOW IN THE RAT KIDNEY: INFLUENCE OF MICROSPHERE SIZE , 1978, Clinical and experimental pharmacology & physiology.

[7]  William Francis Ganong,et al.  Review of Medical Physiology , 1969 .

[8]  T. Amemiya,et al.  Corrosion cast demonstration of retinal vasculature of normal Wistar-Kyoto rats. , 1995, Acta anatomica.

[9]  G. Buckberg,et al.  Total and Regional Myocardial Blood Flow Measurements with 25μ, 15μ, 9μ, and Filtered 1–10μ Diameter Microspheres and Antipyrine in Dogs and Sheep , 1974 .

[10]  M. Araie,et al.  Validation of scanning laser Doppler flowmetry for retinal blood flow measurements in animal models , 2002, Current eye research.

[11]  F. Prinzen,et al.  Blood flow distributions by microsphere deposition methods. , 2000, Cardiovascular research.

[12]  A. Bill,et al.  The microsphere method for measuring low blood flows: theory and computer simulations applied to findings in the rat cochlea. , 1987, Acta physiologica Scandinavica.

[13]  A. Alm,et al.  Radioactively labelled microspheres in regional ocular blood flow determinations. , 1977, Bibliotheca anatomica.

[14]  L. Lind,et al.  EFFECTS OF NITRIC OXIDE SYNTHASE INHIBITION AND ENDOTHELIN ETA RECEPTOR BLOCKADE ON HAEMODYNAMICS IN HYPERTENSIVE RATS , 1998, Clinical and experimental pharmacology & physiology.

[15]  A M Rudolph,et al.  The Circulation of the Fetus in Utero: Methods For Studying Distribution of Blood Flow, Cardiac Output And Organ Blood Flow , 1967, Circulation research.

[16]  Dao-Yi Yu,et al.  Model of endothelin-1-induced chronic optic neuropathy in rat. , 2004, Investigative ophthalmology & visual science.

[17]  J I Hoffman,et al.  Some sources of error in measuring regional blood flow with radioactive microspheres. , 1971, Journal of applied physiology.

[18]  M. Lyon,et al.  Rat Utricular Macula: Blood Flow and Stereological Assessment of Capillary Morphology , 1993, The Annals of otology, rhinology, and laryngology.

[19]  R W Glenny,et al.  The 400 microsphere per piece "rule" does not apply to all blood flow studies. , 2000, American journal of physiology. Heart and circulatory physiology.

[20]  J. Saumet,et al.  New method of cardiac output measurement using ultrasound velocity dilution in rats. , 2001, Journal of applied physiology.

[21]  P. Carlsson,et al.  Multiple Injections of Coloured Microspheres for Islet Blood Flow Measurements in Anaesthetised Rats: Influence of Microsphere Size , 2002, Upsala journal of medical sciences.

[22]  S. Chien,et al.  Effects of sphere size and injection site on regional cerebral blood flow measurements. , 1983, Stroke.

[23]  T. Amemiya,et al.  Microvascular architecture of the rat choroid: Corrosion cast study , 2001, The Anatomical record.

[24]  H. Wässle,et al.  Immunocytochemical identification of cone bipolar cells in the rat retina , 1995, The Journal of comparative neurology.

[25]  R. S. Reneman,et al.  Development of a novel fluorescent microsphere technique to combine serial cerebral blood flow measurements with histology in the rat , 2003, Journal of Neuroscience Methods.

[26]  C. Kilo,et al.  Increased ocular blood flow and 125I-albumin permeation in galactose-fed rats: inhibition by sorbinil. , 1988, Investigative ophthalmology & visual science.

[27]  S. Egginton,et al.  Development of the Fluorescent Microsphere Technique for Quantifying Regional Blood Flow in Small Mammals , 1999, Experimental physiology.

[28]  M. Noble,et al.  Total and Regional Coronary Blood Flow Measured by Radioactive Microspheres in Conscious and Anesthetized Dogs , 1969, Circulation research.

[29]  David G. Cogan,et al.  Retinal Vascular Patterns: Part II. Human Retinal Vessels Studied in Three Dimensions , 1961 .

[30]  A. P. Shepherd,et al.  Microsphere passage through intestinal circulation: via shunts or capillaries? , 1985, The American journal of physiology.

[31]  E. Frohlich,et al.  Regional blood flows measured in conscious rats by combined Fick and microsphere methods. , 1978, The American journal of physiology.

[32]  J. Morrison,et al.  Effect of general anesthetics on IOP in rats with experimental aqueous outflow obstruction. , 2000, Investigative ophthalmology & visual science.

[33]  R. Glenny,et al.  Intravital microscopic observations of 15-microm microspheres lodging in the pulmonary microcirculation. , 2005, Journal of applied physiology.

[34]  U. Zwiener,et al.  Validation of the multiple colored microsphere technique for regional blood flow measurements in newborn piglets , 1997, Basic Research in Cardiology.

[35]  N. Kobayashi,et al.  Effects of intra-atrial injection of colored microspheres on systemic hemodynamics and regional blood flow in rats. , 1994, The American journal of physiology.

[36]  R. Glenny,et al.  Fluorescent microspheres are superior to radioactive microspheres in chronic blood flow measurements. , 1998, American journal of physiology. Heart and circulatory physiology.

[37]  S. Hayreh Evaluation of Optic Nerve Head Circulation: Review of the Methods Used , 1997, Journal of glaucoma.

[38]  S. Roth,et al.  Ischemic preconditioning attenuates hypoperfusion after retinal ischemia in rats. , 1999, Investigative ophthalmology & visual science.

[39]  R. Linsenmeier,et al.  Measurement of blood flow through the retinal circulation of the cat during normoxia and hypoxemia using fluorescent microspheres. , 2001, Microvascular research.

[40]  D. Goldblum,et al.  Cytoarchitecture of the retinal ganglion cells in the rat. , 2002, Investigative ophthalmology & visual science.

[41]  F W Prinzen,et al.  Developments in non-radioactive microsphere techniques for blood flow measurement. , 1994, Cardiovascular research.

[42]  A. Alm Radioactively labelled microspheres in regional cerebral blood flow determinations. A study on monkeys with 15 and 35 mum spheres. , 1975, Acta physiologica Scandinavica.

[43]  O. Kayikcioglu,et al.  Histopathologic effect of chronic use of sildenafil citrate on the choroid & retina in male rats. , 2003, The Indian journal of medical research.

[44]  E. Granstam,et al.  Involvement of nitric oxide in the regulation of regional hemodynamics in streptozotocin-diabetic rats. , 2003, Physiological research.

[45]  K. Messmer,et al.  Methodological error and spatial variability of organ blood flow measurements using radiolabeled microspheres , 1991, Research in experimental medicine. Zeitschrift fur die gesamte experimentelle Medizin einschliesslich experimenteller Chirurgie.

[46]  R W Glenny,et al.  Hemodynamic effects of 15-microm-diameter microspheres on the rat pulmonary circulation. , 2000, Journal of applied physiology.

[47]  S. Wu,et al.  Adler's Physiology of the Eye , 2002 .

[48]  D. Casellas,et al.  Microsphere size and determination of intrarenal blood flow distribution in the rat , 1979, Pflügers Archiv.