Metabolic processes involving strontium (Sr) are the focus of current research because of strontium’s ability to be retained in the bones as a calcium analog. In addition, fall-out substances contain significantly high quantities of strontium, a phenomenon that necessitates further investigations on the topic.
Experiments involving the administration of food samples containing predetermined amounts of Sr to several subjects reveal that high volumes of Sr are absorbed into the body. Approximately 0.2 of the total Sr in the food is incorporated into the subjects’ tissues. Significantly high quantities of Sr are absorbed after simulated fall-outs as compared to local fall-outs following the administration of SrCl to a number of subjects.
Several aspects including the level of glucose present in blood and the nutritive value of food modulate the absorption of strontium in human bodies. For example, the presence of minerals such as calcium, phosphorous and magnesium tend to escalate the rate of Sr absorption by the tissues. In addition, diets containing high proportions of milk constituents and vitamin D raise Sr absorption. Fasting plays a vital role in influencing the concentration of glucose in blood and the rate of Sr absorption.
Studies by McAughey et al. reveal that an all night fast doubles the absorption of Sr. This observation is evident after comparing the Sr absorption of four subjects who ingest Sr-containing substances after fasting with the absorption of an individual who ingests Sr after taking breakfast. A three-fold reduction of calcium intake causes a two-fold increase in Sr absorption.
A comparison of animal and human studies on Sr absorption gives similar outcomes. However, when Sr is administered to rodents as a titanate (SrTiO3) the rate of absorption is relatively low and gives a rate of 0.01 in contrast with the rate of 0.1 when Sr is issued as SrCl.
Age is also thought to play a role in the absorption or Sr. A study by Widdowson et al. in 1960 reveals that the rate of Sr absorption in infants is extremely high at a level of 0.7. It is possible that milk, which is the key diet in infants, contributes to the high levels of Sr absorption since milk rich diets elevate Sr absorption. However, in children between the ages of five and fifteen the rate of Sr absorption is similar to that in adults.
Rodent experiments, in addition, reveal an absorption rate of 0.95 in 31 2-week old rats. Conversely, the absorption values decline to about 0.74 in a sample of five 22-days old rats. Therefore, it can be concluded from these two experiments that Sr absorption declines with an increase in the age of the subject. The probable reason for the high absorption rates in infants is that there is no delay in the transfer of the absorbed Sr to blood. This is because of minimal retention of Sr in the walls of the small intestines.
A systemic biokinetic prototype for alkaline earth metals unequivocally replicates the excretion of Sr through the gastrointestinal tract. The dispensation of radiostrontium through an intravenous injection shows that a quarter of the injected Sr is exuded into the alimentary canal thereby contributing to the endogenous loss of Sr. Excretion through bile accounts for a tiny fraction of the entire secretion of Sr into the alimentary canal.
The ICRP biokinetic model for strontium displays the systemic secretion of Sr as the transfer of blood plasma to the constituents of the large intestines in the upper region of the alimentary canal. This is a simplified version of the whole process, which clearly explains the movement of Sr in biological systems.