Stimulated osteoclastic and suppressed osteoblastic activity in metabolic but not respiratory acidosis.
When bone is cultured in acidic medium produced by a reduced bicarbonate concentration ([HCO(3-)]), a model of metabolic acidosis, there is greater net calcium efflux than when the same decrement in pH is produced by an increased partial pressure of carbon dioxide (PCO2), a model of respiratory acidosis. To determine the effects of metabolic and respiratory acidosis on bone cell function we cultured neonatal mouse calvariae for 48 h under control conditions (pH approximately 7.40, PCO2 approximately 41 mmHg, [HCO(3-)] approximately 25 meq/l) or under isohydric acidic conditions simulating metabolic (pH approximately 7.09, [HCO(3-)] approximately 12) or respiratory (pH approximately 7.10, PCO2 approximately 86) acidosis and measured osteoblastic collagen synthesis and alkaline phosphatase activity and osteoclastic beta-glucuronidase activity. Collagen synthesis was inhibited by metabolic (23.2 +/- 1.3 vs. 30.3 +/- 1.0% in control) but was not altered by respiratory (32.3 +/- 0.6) acidosis. Alkaline phosphatase activity was inhibited by metabolic (402 +/- 16 vs. 471 +/- 15 nmol P.min-1.mg protein-1 in control) but not altered by respiratory (437 +/- 25) acidosis. beta-Glucuronidase activity was stimulated by metabolic (1.02 +/- 0.06 vs. 0.78 +/- 0.05 micrograms phenolphthalein released.bone-1.h-1 in control) but not altered by respiratory (0.73 +/- 0.06) acidosis. Net calcium efflux in control was increased by metabolic (783 +/- 57 vs. 20 +/- 57 nmol.bone-1.48 h-1 in control) and by respiratory (213 +/- 45) acidosis; however, calcium efflux with metabolic was greater than with respiratory acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Bushinsky
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DA
Department of Medicine, University of Rochester School of Medicine and Dentistry, New York 14618.
D000138:Acidosis / Q000201:enzymology* / Q000473:pathology; D000142:Acidosis, Respiratory / Q000201:enzymology* / Q000473:pathology; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D003094:Collagen / Q000096:biosynthesis; D005966:Glucuronidase / Q000378:metabolism; D051379:Mice; D009924:Organ Culture Techniques; D010006:Osteoblasts / Q000201:enzymology*; D010010:Osteoclasts / Q000201:enzymology*
D003094:Collagen; D000469:Alkaline Phosphatase; D005966:Glucuronidase