title: Regional blood flow during simulated diving in the conscious Weddell seal.
abstract: Changes in regional blood flow during simulated normobaric diving were studied in the conscious Antarctic Weddell seal (Leptonychotes weddelli) by injecting 25-microns radioactive microspheres into the left ventricle. Injections were performed before and 8--12 min after submersion of the head in iced seawater. Diving was associated with a fall in cardiac output from a mean control value of 39.8 +/- 10.2 to 5.6 +/- 3.4 l/min (mean +/- SD) and in heart rate from 52 +/- 15 to 15 +/- 4 beats/min. Blood flow to the splanchnic and peripheral vascular bed was reduced by more than 90%, cerebral blood flow was unchanged, right and left ventricular blood flow decreased by 85%, and adrenal blood flow decreased by 39%. The pulmonary fraction of the injected microsphere dose increased from 7.9 to 29.9% during diving. This may signify a large increase of peripheral arteriovenous shunting during the dive and/or increased bronchial artery blood flow. It is concluded that blood flow during diving is directed to organs and tissues according to their metabolic requirements.
mesh_terms: D000818:Animals; D001775:Blood Circulation; D001794:Blood Pressure; D010872:Caniformia / Q000502:physiology*; D002302:Cardiac Output; D004242:Diving; D008863:Microspheres; D011868:Radioisotopes; D046048:Seals, Earless / Q000502:physiology*
chemical_list: D011868:Radioisotopes