Second international conference on strontium metabolism

Warren, Janet Mary (1973) Second international conference on strontium metabolism. PhD thesis, University of Glasgow.

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Abstract

The main object of the work was to study the mechanisms of discrimination in the transfer of strontium and calcium across biological membranes. 3. The experimental work was done in rats and in human subjects using radioactive and stable tracers and intravenous and oral doses of stable strontium. All experiments were carried out under in vivo conditions. 4. The studies using the rat as experimental animal investigated the passage of stronttum-85 with respect to calcium-47 across the gastrointestinal membrane from the bloodstream to the intestine. The isotopes were given intravenously and the rats were examined both feeding and fasting. From the first study which was over a 24 hour interval it appeared that strontium was excreted to a slightly greater extent than calcium into the intestine during feeding. When the rats were fasted, less of both isotopes was excreted by this route although the difference between strontium and calcium was increased. The Sr/Ca faecal excretion ratio increased from 1.2 in the feeding rats to 2,2 in the fasting animals, Intravenously administered strontium-85 was excreted equally in urine and faeces - approximately 10% of the dose by each route of excetion. Calcium-47 however was mainly excreted in stool (approximately 8%) while less than 1% was excreted via the kidney. Fasting caused reduced levels of both 85Sr and 47Ca in the urine. These excretory differences resulted in (a) greater bone deposition of 47Ca than 85Sr both during feeding and fasting and (b) greater levels of both isotopes in the skeleton of the fasting rats than of the feeding animals. A second rat study was performed to investigate the effect of time on the distribution of the isotopes compared to the 24 hour study. In this case animals were sacrificed at 0.5, 1, 2 and 4 hours after injection of the dose. The results of this experiment indicate that calcium is excreted into the intestine slightly faster than strontium and the differences between 85Sr and 47Ca at 24 hours were due to discrimination in reabsorption by the gut. It appeared that there was little difference between the isotopes between 1 and 4 hours. In fasting the reabsorption of the secreted isotopes was greater than during feeding. The passage of strontium with respect to calcium across the human placenta was investigated. Neutron activation techniques were used to measure stable strontium and flame emission spectrometry for calcium. It was shown that calcium passes more readily than strontium across the membrane from mother to child by a factor of about 2. The concentration of calcium in the serum of the newborn was about 20% higher than that of the mother. The effect of stable strontium on the excretions of strontium and calcium was studied in man during both oral and intravenous administration of the element. It was shown that a large dose of stable strontium administered orally was similarly distributed in the excretions as was the trace level of an average diet. Retention of such a dose was for a short period of time in a subject who had no error in calcium metabolism. Intravenously administered stable strontium was mainly excreted via the kidney. Ammonium Chloride and Aluminium Phosphate Gel have been used in attempts to modify stable strontium excretion but with little success. Both intravenously and orally administered stable strontium had a marked effect on the urinary calcium excretion. This was reduced to about half of the normal level when strontium was administered by either route.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J H Hutchinson
Keywords: Physiology
Date of Award: 1973
Depositing User: Enlighten Team
Unique ID: glathesis:1973-72834
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06
URI: http://theses.gla.ac.uk/id/eprint/72834

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