title: Diurnal rhythm in serum activity of wheat-germ lectin-precipitable alkaline phosphatase: temporal relationships with the diurnal rhythm of serum osteocalcin.
abstract: Serum levels of osteocalcin (S-OC) and lectin-precipitable alkaline phosphatase activity (S-LAP) are sensitive markers of osteoblastic activity. Diurnal variation has been found for S-OC but has not been reported for S-LAP. We measured S-LAP and serum total alkaline phosphatase (S-TAP) in samples drawn every 60 min during a 24-h study period in nine normal subjects and correlated the findings with the diurnal variation in S-OC. A significant (p less than 0.05) diurnal variation in S-LAP characterized by peaks at 1430 hours and 2330 hours and nadir at 0630 hours was found. Peak levels were 30% higher than nadir level (p less than 0.05). S-TAP also varied significantly (p less than 0.05) with nadir at 0630 hours, showing a difference of 23% between peak and nadir levels (p less than 0.05). Significant cross-correlation was found between S-OC and S-LAP and S-TAP when these lagged 4 h after S-OC: r = 0.51 (p less than 0.02) and r = 0.65 (p less than 0.003), respectively. In other words, changes in S-LAP and S-TAP preceded changes in S-OC by 4 h. There were no significant cross-correlations between the non-lectin-precipitable fraction of AP and S-OC. In conclusion, S-LAP varies in a diurnal rhythm closely related with the diurnal rhythm of S-OC. The almost similar patterns in the diurnal serum levels of these two osteoblastic products strongly suggest that osteoblastic activity fluctuates rhythmically during the day in humans.
authors.affiliation: University Department of Endocrinology and Metabolism, Aarhus Amtssygehus, Denmark.
authors.forename: H K
authors.initials: HK
authors.lastname: Nielsen
authors.forename: K
authors.initials: K
authors.lastname: Brixen
authors.forename: L
authors.initials: L
authors.lastname: Mosekilde
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood*; D011232:Chemical Precipitation; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000097:blood*; D008297:Male; D015675:Osteocalcin / Q000097:blood*; D014909:Wheat Germ Agglutinins / Q000494:pharmacology
chemical_list: D007527:Isoenzymes; D014909:Wheat Germ Agglutinins; D015675:Osteocalcin; D000469:Alkaline Phosphatase