A comparison of the effects of bovine parathyroid hormone 1–34 and methylated prostaglandin E2 analogues on plasma calcium and inorganic phosphate levels in immature chickens and rats

EFFECTS OF SYNTHETIC BOVINE PARATHYROID HORMONE (1‐34) AND ITS ANALOGUES ON 45Ca UPTAKE AND ADENYLATE CYCLASE ACTIVATION IN BONE AND PLASMA CALCIUM LEVELS IN THE CHICK

“…Similarly our results are at variance with those of Robertson, Peacock, Atkins & Webster (1972) who suggested that a decrease in total Ca in media bathing cultured mouse calvaria could be interpreted as a transient increase in Ca uptake into this bone in response to PTH. The responses which we observe could possibly account for the rapid (15 min) hypercalcaemic actions of bPTH(1-34) in chicks and rats (Shaw & Dacke, 1986a). However, native bPTH(I-84) fails to reduce bone 45Ca uptake in chicks (Shaw, 1987) but not rats (Dacke & Shaw, 1987a) at 3-15 min, a finding not entirely consistent with the known hypercalcaemic actions of this molecular species (Kenny & Dacke, 1974).…”

“…It was suggested that rapid (10 min) hypercalcaemic responses to PTH in laying hens might reflect osteoclastic bone resorption. Similar actions could explain rapid hypercalcaemic responses to bPTH(1-34) in chicks and immature rats (Shaw & Dacke, 1986a) and gradients of Ca produced by osteoclastic osteolysis could also lead to net inhibition of bone 45Ca uptake. It is doubtful, however, whether such a mechanism could account for the reduction in femoral "CCa uptake seen within 3 min (Fig.…”

“…Several studies suggest that PTH stimulates bone resorption via primary stimulation of osteoblasts, osteoclastic activity being dependent on either osteoblast-released cytokines (Perry, Skogen, Chappel, Wilner, Kahn & Teitelbaun, 1987) or osteoblast-osteoclast contact (Chambers, 1985). The relevance of these mechanisms to the effects of PTH on bone 45Ca uptake should be considered, particularly since changes in morphology and min of PTH injection into female Japanese quail (Miller, Bowman & Myers, 1984 (Shaw & Dacke, 1986a) and gradients of Ca produced by osteoclastic osteolysis could also lead to net inhibition of bone 45Ca uptake. It is doubtful, however, whether such a mechanism could account for the reduction in femoral "CCa uptake seen within 3 min (Fig.…”