THE DYNAMIC RED CELL STORAGE FUNCTION OF THE SPLEEN IN SHEEP

Abstract

SUMMARY In the sheep the spleen has been shown to act as a dynamic reservoir of highly concentrated blood. As the number of red cells retained in the spleen is dependant upon the emotional state of the animal at the time, the values of the jugular haematocrit and of the F cells ratio are subject to wide variations. The extent to which such variations can affect the calculated values of blood volume (BV) and red cell volume (RCV) from plasma volume (PV) and jugular haematocrit has been demonstrated. Separate determination of RCV by labelled‐cell techniques, such as 51 Cr‐labelling, may also be fallacious, because a considerable proportion of the total red cells (of the order of 10 p.c.) was found to be withheld from free “mixing” in some sheep; but this was readily overcome by the intravenous administration of adrenaline. Little error could result, and considerable saving of time could be made, by basing estimates of RCV and PV on a single sample taken 10 minutes after administration of labelled cells and T‐1824 together with adrenaline to contract the spleen and thereby promote rapid and complete “mixing”. More simply, after injection of only T‐1824 plus adrenaline, BV pl could be calculated from the formula PV/(100 – H × F cells ) where H is the haematocrit determined after 2–3 minutes, PV is based on a single plasma sample at 10 minutes and F cells after adrenaline is taken to be 0·81. The mean PV of 21 determinations on 13 Merino sheep, as determined by the T‐1824 method, was 44·6 ml./kg. (S.D., 3·1 ml./kg.). The mean BV, RCV and PV of 5 sheep, as determined by 51 Cr‐labelled cells and T‐1824, were 66·4, 19·7 and 46·7 ml./kg. respectively (S.D., 5·4, 2·8 and 3·6 ml./kg, respectively).