The vascular origin of slow wave flowmotion in skeletal muscle during local hypotension.
Intravital microscopy (IVM) and laser-Doppler-flowmetry- or fluxmetry (LDF) were used to simultaneously assess periodic hemodynamics (vaso/flowmotion) in the tenuissimus muscle of eleven New Zealand White (NZW)-rabbits during local reduction of arterial pressure. Diameter changes of transverse arterioles (TR) were monitored with the microscope, and in six animals also blood cell velocity measurements were performed with a cross-correlation technique. One LDF was positioned at the tenuissimus muscle as close to the objective as possible without causing optical interference. A second LDF was positioned at the underlying gastrocnemius muscle. Slow wave vaso/flowmotion was not present at control arterial pressure (x = 73 mmHg, range-r: 60-87) but was induced as local femoral pressure was reduced, being minimal at 35 mmHg (r: 20-50). The vaso/flowmotion frequencies of the IVM, tenuissimus-LDF, and the gastrocnemius-LDF signals were in the order of 1.5 cpm. LDF-flowmotion frequencies in the two muscles showed no correlation (R = +0.06, P = 0.4). The IVM flow-frequencies in the TR, however, correlated well with the oscillations recorded with the tenuissimus-LDF placed nearby (R = +0.89, p +0.01). Regular diameter variations were recorded only in the eleven cases where the microscope focused on the proximal portion of the TR; these oscillation frequencies were correlated with corresponding LDF-tenuissimus recordings (R = +0.97, p < 0.01). We conclude that slow wave vasomotion in rabbit skeletal muscle is not present during control conditions, but is induced on a regular basis by local blood pressure reduction and that it originates in the proximal part of the TR as reflected by slow wave flowmotion in LDF.
Department of Applied Mechanics and Engineering Sciences-Bioengineering, University of California, San Diego, La Jolla.
J A
JA
Schmidt
P
P
Borgström
M
M
Intaglietta
D000818:Animals; D001160:Arterioles / Q000033:anatomy & histology; D001783:Blood Flow Velocity; D004912:Erythrocytes / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D007022:Hypotension / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry; D008297:Male; D008853:Microscopy; D009132:Muscles / Q000098:blood supply*; D011817:Rabbits; D013997:Time Factors; D014666:Vasomotor System / Q000502:physiology*