Capillary diameter changes during low perfusion pressure and reactive hyperemia in rabbit skeletal muscle.
Capillary diameter changes were studied in the tenuissimus muscle of 29 urethan-anesthetized New Zealand White rabbits. Capillaries were visualized with transillumination bright-field microscopy (saltwater lens, x 50; resolution approximately 0.3 microns). Median capillary diameter during the control period was 4.4 microns (range 3.2-6.9 microns). Complete aortic occlusion resulted in a reduction of median femoral arterial pressure to 17 mmHg (range 4-22 mmHg). During 2 min of occlusion, capillary diameter decreased by 6%, with greater change on the arteriolar side of the capillary than on the venular side. During reactive hyperemia after release of the occluder, capillary diameter maximally increased by 12% compared with the control period, with a larger response at the arteriolar end of the capillary than at the venular end. Median capillary resistance was estimated to increase by 27% during occlusion and to decrease by 36% during peak reactive hyperemia. The observed diameter changes are compatible with the idea that capillaries change their diameter relative to changes in transmural pressure.
Bosman
J
J
Department of Biophysics, Cardiovascular Research Institute Maastricht, University of Limburg, The Netherlands.
Tangelder
G J
GJ
Oude Egbrink
M G
MG
Reneman
R S
RS
Slaaf
D W
DW
D000818:Animals; D001018:Aortic Diseases / Q000503:physiopathology; D001783:Blood Flow Velocity; D001810:Blood Volume; D002196:Capillaries / Q000502:physiology; D003251:Constriction, Pathologic; D004912:Erythrocytes / Q000502:physiology; D005260:Female; D006940:Hyperemia / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply*; D010477:Perfusion; D011312:Pressure; D011817:Rabbits; D014655:Vascular Resistance; D014664:Vasodilation