Bone blood flow measured by 85 Sr microspheres and bone seeker clearances in the rat

blood flow measured by Vr microspheres and bone seeker clearances in the rat. Am. J. Physiol. 236(l): Hl-H6, 1979 or Am. J. Physiol.: Heart Circ. Physiol. 5(l): Hl-H6, 1979.-This paper investigates further the relationship between the initial bone clearance of a bone-seeking radioisotope or labeled sub-stance and the bone blood flow. The bone blood flow of rats was modified over the widest possible range of physiological values by heating and cooling their hindlimbs. Osseous blood flow was measured by the arteriolar trapping of labeled microspheres of 15 pm diameter injected into the left ventricle. The plasma clearances of 45Ca and 99 m Tc by bone were measured 10 min after the intravenous injection of radiocal-cium and of 99 m technetium pyrophosphate. The extraction ratio for 45Ca over the lO-min interval (Va clearance/bone plasma flow) was 0.60 for low blood flows, 0.40 for blood flow