Body composition on 15 of these seals also was
determined using the labeled-water dilution method. Initial
blood samples were collected from the extradural vein in
serum vacutainers (no anticoagulant) for determination of
background isotope levels. Seals were given an injection of
1.5 mCi of tritiated water (HTO) and serial blood samples
were collected in serum vacutainers at 15–30 min intervals up to 1.5–3 h post-injection to determine equilibration
time. Equilibration occurred within 90 min (Fig. 2), so
samples collected after 90 min were averaged and used as
the equilibrium value. Blood samples were centrifuged and
serum was collected for total body water determination.