title: The effect of long-term administration of alpha 1-blocker prazosin on capillary density in cardiac and skeletal muscle.
abstract: The effect of prazosin on heart and muscle blood flow and capillary density was studied in rats. In acute experiments, alpha 1-blocker prazosin almost trebled blood flow in fast skeletal muscles [tibialis anterior (TA) and extensor digitorum longus (EDL)], but did not affect coronary flow when infused i.v. at a dose of 0.5 microgram.ml-1.min-1 for 30 min. Prazosin in an equivalent dose was then given orally over a period of 5 weeks to investigate its effect on capillarisation in heart and skeletal muscle. Capillary density (CD, capillaries.mm-2), estimated in frozen sections stained for alkaline phosphatase, was similar in the hearts of prazosin-treated and control rats. Capillary/fibre ratio in skeletal muscles increased from 1.52 +/- 0.019 in control EDL to 1.69 +/- 0.01 (P less than 0.001) and from 1.56 +/- 0.04 in control TA to 2.16 +/- 0.04 (P less than 0.001). In TA, the increase was greater than in EDL both in the glycolytic periphery (from 1.30 +/- 0.13 to 1.75 +/- 0.11, P less than 0.025) and the oxidative core of the muscle (from 1.837 +/- 0.14 to 2.51 +/- 0.12, P less than 0.005). Unilateral crush of the lateral peroneal nerve and subsequent reinnervation over the next 7 weeks resulted in redistribution of fibre types from a typical mosaic pattern into groups composed of fibres of similar oxidative capacity. Capillary density as well as capillary/fibre ratio in purely glycolytic areas was lower when compared to supply of glycolytic fibres in normal muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, University of Birmingham, UK.
authors.forename: A
authors.initials: A
authors.lastname: Ziada
authors.forename: O
authors.initials: O
authors.lastname: Hudlicka
authors.forename: K R
authors.initials: KR
authors.lastname: Tyler
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002196:Capillaries / Q000033:anatomy & histology / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000187:drug effects*; D006321:Heart / Q000033:anatomy & histology / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009132:Muscles / Q000098:blood supply* / Q000187:drug effects / Q000294:innervation; D009409:Nerve Crush; D009929:Organ Size / Q000187:drug effects; D011224:Prazosin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow / Q000187:drug effects
chemical_list: D011224:Prazosin