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Title: Studies on the effects of parathyroid hormone and prostaglandins on bone and calcium metabolism in chicks and immature rats in vivo
Author: Shaw, A. J.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1987
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1. Investigations have been carried out into mechanisms underlying rapid hypercalcaemic actions of parathyroid hormone (PTH) and prostaglandins (PGs) in chicks (12 day old), and in a limited parallel study, immature (4 week old) rats in vivo. 2. Intravenous (i.v.) injection of synthetic bPTH(1-34) (3.3μg/100g body wt.) or 16,16-dimethyl PGE_2 (5-20μg/100g body wt.) caused hypercalcaemia within 15 minutes in chicks. The PG, but not PTH, also elevated plasma Pi levels at early (15-90 min.) time intervals in chicks. Similar but less sensitive plasma Ca and Pi responses occurred following i.v. injection of these agents into rats. bPTH(1-34) and 16,16-dimethyl PGE2 had little effect on plasma osmolality in chicks, indicating the relative specificity of their actions on plasma Ca and Pi. 3. Studies were carried out using a combination of acute 45Ca labelling (injected i.v. with hormone) and microwave fixation to stabilize tissue isotope levels after death. In the absence of hormones, 45Ca was rapidly taken up by the skeleton in preference to a variety of soft tissues. Bone and soft tissue 45Ca uptake was greater in non-microwaved compared with microwave fixed chicks. 4. bPTH(1-34) (0.36-3.3μg/100g body wt.), 16,16-dimethyl PGE_2 (0.55-5μg/100g body wt.), and a range of natural PGs (PGE2, PGE1, PGF, PGI2) (5-20μg/100g body wt.) each inhibited net ^45Ca uptake by femur and calvarium within 3 minutes in chicks. Purified bPTH(1-84) (10μg/100g body wt.) and synthetic hPTH(1-34) (3.3μg/100g body wt.) also showed a tendency to inhibit chick bone net ^45Ca uptake at early (3-15 min.) time intervals. Responses to bPTH(1-34) and 16,16-dimethyl PGE_2 were reflected by plasma retention of the acutely injected ^45Ca label compared with controls.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available