Summary
The adhesion and detachment of platelets on surface-bound albumin and surface-bound
fibrinogen were studied. Fluorescent video-microscopy of platelets labelled with mepacrine
was used to provide continuous information. Glass tubes (I.D. 1.3 mm) were precoated
with either human albumin or human fibrinogen before exposure to a suspension of washed
platelets and red cells. Observations were made 0.5 cm from the tube’s entrance over
a 1370 μm2 portion of lumen. The rate at which cells leave the measurement area and the percent
of initially attaching cells which leave are independent of protein coating but increase
with flow rate. The percent of initially attaching platelets which permanently adhere
is equal for both protein coatings but the pathways leading to this result can be
different. For the lower shear rate studied, 80 s−1, the percent of cells which permanently adhere on first contact is less for albumin
than for fibrinogen; the percent of initially attaching cells which adhere and then
move before permanent adhesion is greater for albumin. The mechanism of detachment
and reattachment leads to the equality of the overall adhesion efficiencies for the
two protein coatings at 80 s−1. For the higher shear rate studied, 456 s−1 the adhesion pathways for both coatings were the same.
Key words
Albumin - Fibrinogen - Platelet adhesion - Mepacrine
