Influence of blood calcium on calcitonin receptors in isolated chick osteoclasts.
Isolated osteoclasts obtained from young chickens fed a normal (+Ca) or deficient (-Ca) calcium and vitamin D diet for 3 weeks, were studied for their ability to bind salmon calcitonin (sCT). Osteoclasts obtained from -Ca chickens, when incubated with 0.1 mumol sCT/l, doubled cyclic (c)AMP production and retracted from a glass support, as observed by scanning electron microscopy. The presence of receptors was also demonstrated by autoradiography and competition analysis of 125I-labelled sCT binding. The number of receptors per cell was 0.9 +/- 0.1 x 10(4). In contrast, osteoclasts obtained from +Ca chickens did not increase cAMP production and did not retract in the presence of 0.1 mumol sCT/l. No specific binding of 125I-labelled sCT could be demonstrated on these osteoclasts. Plasma levels of calcium and calcitonin were measured in +Ca and -Ca chickens. The plasma concentration of calcium was markedly lower at 3 weeks in -Ca than in +Ca chickens. The plasma concentration of calcitonin was decreased in -Ca chickens compared with +Ca chickens at the first week and kept decreasing during the 3 weeks. These results strongly support the hypothesis that calcium and vitamin D intake regulate plasma calcitonin levels in chickens, and that calcitonin receptors can be detected on chicken osteoclasts only when blood calcium is decreased by a diet deficient in calcium and vitamin D.
Eliam
M C
MC
INSERM U18, Hôpital Lariboisière, Paris, France.
Baslé
M
M
Bouizar
Z
Z
Bielakoff
J
J
Moukhtar
M
M
de Vernejoul
M C
MC
D000818:Animals; D002116:Calcitonin / Q000097:blood; D002118:Calcium / Q000097:blood* / Q000172:deficiency; D000242:Cyclic AMP / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D010010:Osteoclasts / Q000378:metabolism* / Q000648:ultrastructure; D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface / Q000032:analysis*; D014808:Vitamin D Deficiency / Q000378:metabolism
D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface; D002116:Calcitonin; D000242:Cyclic AMP; D002118:Calcium