Low venular shear rates promote leukocyte-dependent recruitment of adherent platelets.
The influence of reductions in venular shear rate on platelet-endothelial (P/E) cell adhesion has not been previously addressed. The objectives of this study were to define the effects of reductions in venular shear rate on P/E cell adhesion and to determine the interdependence of P/E cell adhesion and leukocyte-endothelial (L/E) cell adhesion at low shear rates. Intravital videomicroscopy was used to quantify P/E and L/E cell adhesion in rat mesenteric venules exposed to shear rates ranging between 118 +/- 9 and 835 +/- 44 s(-1). Shear rate was altered in postcapillary venules by rapid, graded blood withdrawal, without retransfusion of shed blood. Reducing shear rate from >600 s(-1) to <200 s(-1) resulted in an eightfold increase in L/E cell adhesion, whereas P/E cell adhesion increased 18-fold. A blocking antibody directed against P-selectin blunted both the P/E and L/E cell adhesion elicited by low shear rates. Immunoneutralization of CD11/CD18 on leukocytes or rendering animals neutropenic also blocked the shear rate-dependent recruitment of both platelets and leukocytes. These findings indicate that 1) low shear rates promote P/E and L/E cell adhesion in mesenteric venules, and 2) adherent neutrophils (mediated by CD11/CD18) create a platform onto which platelets can bind to the venular wall at low shear rates.
Russell
Janice
J
Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport 71130-3932, USA.
Cooper
Dianne
D
Tailor
Anitaben
A
Stokes
Karen Y
KY
Granger
D Neil
DN
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001792:Blood Platelets / Q000502:physiology*; D018821:CD18 Antigens / Q000276:immunology; D005434:Flow Cytometry; D007962:Leukocytes / Q000502:physiology*; D008297:Male; D018715:Microscopy, Video; D019007:P-Selectin / Q000276:immunology; D010973:Platelet Adhesiveness / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000503:physiopathology*; D013152:Splanchnic Circulation / Q000502:physiology; D013314:Stress, Mechanical; D014699:Venules / Q000502:physiology*
D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D019007:P-Selectin