Metabolism of Ca and Sr in Late Adult Life

Abstract

Data are presented on the metabolism of Ca and Sr in a healthy male volunteer who, in a series of investigations conducted between the ages of 53 and 82 y, received controlled intakes of 45Ca, 47Ca, or 85Sr. No age-related trends were established, either in factors affecting the skeletal deposition of the tracers or in their subsequent retention studied for up to 462 d after intake. The data thus lend support to an important working postulate in the ICRP's model of alkaline earth metabolism.

Immune System Modifications Induced in a Mouse Model of Chronic Exposure to90Sr

“…In three healthy subjects that received a single oral dose of SrCl 2 , the estimated average wholebody elimination half-times, estimated over 13 days, were 2 (30%) and 59 days (70%) (Uchiyama et al 1973). Similar short-term rates of elimination have been observed within days to a few weeks after an intravenous injection of SrCl 2 (MacDonald et al 1965;Newton et al 1990). …”

“…The urine:fecal excretion ratio of 3 that was observed in the radium dial workers is consistent with ratios of 2-6 observed several days to weeks after subjects received an intravenous injection of SrCl 2 (Bishop et al 1960;Blake et al 1989aBlake et al , 1989bLikhtarev et al 1975;Newton et al 1990;Samachson 1966;Snyder et al 1964;Uchiyama et al 1973). Thus, urine appears to be the major route of excretion of absorbed strontium.…”

“…The renal clearance of strontium has been measured in human subjects who received an intravenous injection of a dose of SrCl 2 and is approximately 4-10 L/day and 2-3 times greater than renal calcium clearance (Blake et al 1986(Blake et al , 1989a(Blake et al , 1989bHarrison et al 1955Harrison et al , 1966aNewton et al 1990;Samachson 1966). Based on these estimates, the renal clearance of strontium is substantially less than the product of the glomerular filtration rate in humans (approximately 180-200 L/day) and the estimated rate of filtration of strontium, assuming that approximately 50% of the strontium in plasma is ultrafilterable (Harrison et al 1955).…”

Reliability of Current Biokinetic and Dosimetric Models for Radionuclides: A Pilot Study

“…A common removal half-time of 1 d is assigned to all four elements, based on the same data as considered in estimating the deposition fraction for bone surfaces, plus measurements of the early decline in whole-body retention of intravenously injected radioactive calcium, strontium, barium, or radium in human subjects (Spencer et al 1960;Bishop et al 1960;Heaney et al 1964;Harrison et al 1967;Phang et al 1969;Carr et al 1973;Likhtarev et al 1975;Malluche et al 1978;Henrichs et al 1984;Newton et al 1990Newton et al , 1991 coupled with measurements of soft-tissue retention as described earlier. A removal half-time of 1 d refers to the half-time that one theoretically would observe if recycling of activity to bone surfaces could be stopped.…”

“…Based on data for human subjects injected with radioisotopes of calcium, strontium, barium, or radium (Spencer et al 1960;Bishop et al 1960;Heaney et al 1964;Harrison et al 1967;Phang et al 1969;Carr et al 1973;Likhtarev et al 1975;Malluche et al 1978;Henrichs et al 1984;Newton et al 1990Newton et al , 1991, it was concluded that the fraction of injected activity released from bone over the intermediate term (and thus assigned to exchangeable bone volume) is roughly one-sixth of activity leaving bone surfaces for all four elements.…”