title: Vertical distribution of elements in cells and matrix of epiphyseal growth plate cartilage determined by quantitative electron probe analysis.
abstract: Quantitative electron probe analysis was performed on chick epiphyseal growth cartilage prepared by two anhydrous methods, ultrathin cryosections and freeze-dried epoxy-embedded tissue. Levels of Na, Mg, P, S, Cl, K, and Ca were determined in cytoplasm, mitochondria, extracellular matrix, matrix vesicles, and mineral nodules in four zones of the cartilage--proliferative, prehypertrophic, early hypertrophic, and early calcification. The exceptionally high levels of Na and K (up to 550 and 200 mmol/kg wet wt, respectively) found in the matrix are believed to be largely bound to fixed anions. Within cells, Na was higher than K (140 versus 20-34 mmol/kg wet wt), a condition that may reflect hypoxia. Ca and P were low in cells and unmineralized matrix. Ca and P were high in mitochondrial granules of the early hypertrophic zone and diminished in amount in the calcifying zone; the converse occurred in matrix vesicles. Mg was low to undetectable except in heavily mineralized structures (i.e., mitochondrial granules, matrix vesicles, and mineral nodules). S levels were high in matrix (approximately 400 mmol/kg wet wt) and increased slightly with maturation. The amount of S present greatly exceeds Ca levels and implies that sulfate, the predominant form of sulfur in proteoglycans, may serve as an ion-exchange mechanism for the passage of Ca through the matrix to sites where Ca and phosphate are precipitated.
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis; D002645:Chickens; D002713:Chlorine / Q000032:analysis; D003593:Cytoplasm / Q000032:analysis; D004577:Electron Probe Microanalysis; D005109:Extracellular Matrix / Q000032:analysis; D006132:Growth Plate / Q000032:analysis* / Q000166:cytology; D066298:In Vitro Techniques; D008274:Magnesium / Q000032:analysis; D008928:Mitochondria / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D011188:Potassium / Q000032:analysis; D012964:Sodium / Q000032:analysis; D013455:Sulfur / Q000032:analysis
chemical_list: D010758:Phosphorus; D002713:Chlorine; D013455:Sulfur; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium