Calcium transport in isolated bone cells. III. Effects of parathyroid hormone and cyclic 3',5'-AMP.
The effects of parathyroid hormone (PTH) and cyclic 3',5'-AMP (cyclic AMP) on calcium transport were studied in isolated bone cells. Bone cells were isolated by collagenase digestion of 20-21 day old fetal rat calvaria. Calcium transport was measured with 45Ca. PTH (0.2 mug/ml) increased calcium uptake 30--40% over control values at 37 C. At 4 C, the effects were magnified and 70--170% increases in calcium uptake were observed. The effects were present 1--10 minutes after the simultaneous addition of hormone and 45Ca. PTH had no effect on calcium efflux. Neither dibutyryl cyclic AMP (10(-4)-10(-3)M) nor cyclic AMP (10(-7)-3 X 10(-6)M) had any effect on calcium uptake or efflux. Methylisobutylxanthine (0.1 mM) caused no change in calcium uptake although increase in cyclic AMP were noted. The characteristic PTH-induced increase in cyclic AMP seen at 37 C was not observed at 4 C. It is postulated that PTH increases the permeability of bone cell membranes to calcium. At 4 C the membrane is relatively impermeable so the PTH effect is magnified. The PTH-induced increase does not appear to be mediated through cyclic AMP.
D000818:Animals; D001693:Biological Transport, Active; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology*; D005260:Female; D005333:Fetus; D066298:In Vitro Techniques; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011247:Pregnancy; D051381:Rats; D014970:Xanthines / Q000494:pharmacology
D010281:Parathyroid Hormone; D014970:Xanthines; D003994:Bucladesine; D000242:Cyclic AMP; D002118:Calcium