title: Hydroxyproline in serum as a homeostatic index for calcium in cattle.
abstract: Hydroxyproline, calcium, magnesium, phosphorus, and alkaline phosphatase values were determined in serum over 24 h in Holstein cows. The cows represented two age groups and three percents of diet calcium. Hydroxyproline followed a cyclic pattern dipping at 0800 and 1600 h after milking at 0500 and 1530 h. Phosphorus showed a 24 h rhythm peaking at 1600 h. No other time effects were demonstrated. Hydroxyproline and alkaline phosphatase were both lower in the older cows, indicating a decreased calcium mobilization from bone with age. There was a correlation coefficient of only .20 between serum calcium and hydroxyproline. The calcium concentration in serum was maintained within a narrow range presumably as a result of homeostatic mechanisms involving bone resorption, i.e. the release of calcium and hydroxyproline may indicate the degree of homeostasis required to maintain serum calcium.
mesh_terms: D000367:Age Factors; D000469:Alkaline Phosphatase / Q000097:blood; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002136:Calcium, Dietary; D002417:Cattle / Q000378:metabolism*; D002940:Circadian Rhythm; D004305:Dose-Response Relationship, Drug; D005260:Female; D006706:Homeostasis; D006909:Hydroxyproline / Q000097:blood*; D007774:Lactation; D008274:Magnesium / Q000097:blood; D010758:Phosphorus / Q000097:blood; D011247:Pregnancy
chemical_list: D002136:Calcium, Dietary; D010758:Phosphorus; D000469:Alkaline Phosphatase; D008274:Magnesium; D006909:Hydroxyproline; D002118:Calcium