title: Role of carbonic anhydrase in bone resorption induced by 1,25 dihydroxyvitamin D3 in vitro.
abstract: The present investigation was undertaken to study the role of carbonic anhydrase in 1,25 dihydroxyvitamin D3-induced bone resorption. Calvaria were removed from 5- to 6-day-old mice and cultured for periods up to 96 h in Dulbecco's Modified Eagle Medium (high glucose, 4,500 mg/dl) supplemented with antibiotics and either heat-inactivated horse and fetal calf sera or bovine serum albumin. The experimental cultures contained 1 X 10(-8) M 1,25 dihydroxyvitamin D3 (1,25(OH)2D3). All cultures were incubated at 37 degrees C in 5% CO2/95% air. Bone resorption was assessed by release of stable calcium into the medium. Bone enzymes (acid and alkaline phosphatases and carbonic anhydrase) were determined following homogenization in 0.25 M sucrose. The effects of 1,25(OH)2D3 were studied in the presence and absence of the carbonic anhydrase inhibitor acetazolamide and its analogue (CL 13,850), which lacks inhibitory activity. Acetazolamide inhibited 1,25(OH)2D3-induced calcium release in a dose-dependent fashion from 10(-5)-10(-4)M. When added to the cultures at a concentration of 1 X 10(-4)M, acetazolamide completely blocked the 1,25(OH)2D3-induced calcium release, a phenomenon not seen with an equimolar concentration of CL 13,850. The most significant finding was that 1,25(OH)2D3-induced calcium release was accompanied by a significant increase in the carbonic anhydrase activity of bone at both 48 (treated/control ratio = 2.05) and 96 (treated/control ratio = 2.59) hours.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000135:Acid Phosphatase / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001862:Bone Resorption / Q000139:chemically induced / Q000187:drug effects / Q000201:enzymology*; D001842:Bone and Bones / Q000201:enzymology; D002117:Calcitriol / Q000037:antagonists & inhibitors; D002118:Calcium / Q000378:metabolism; D002256:Carbonic Anhydrases / Q000502:physiology*; D007700:Kinetics; D051379:Mice; D009924:Organ Culture Techniques; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D013449:Sulfonamides; C037272:Cl 13850; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D002256:Carbonic Anhydrases; D002117:Calcitriol; D000086:Acetazolamide; D002118:Calcium