Alkaline Phosphatase Isoenzym es and Osteocalcin in Serum of Norm al Subjects*f

Clinical laboratory tests are increasingly being used to evaluate individ­ uals for osteoporosis and other metabolic bone diseases. Serum bone alka­ line phosphatase (AP) [EC 3.1.3.1, orthophosphoric-m onoester phosphoh y d ro la se (alkaline op tim um )] and osteoca lc in a re u se d to assess osteoblastic activity. Although m ethods for assessing relative amounts of AP isoenzymes continuously appear in the literature, no single m ethod is satisfactory for quantification. Polyacrylamide gel electrophoresis w ith densitom etric scanning com bined with two-point heat inactivation was used to obtain quantitative values for AP isoenzymes. Serum bone AP concentrations correlated positively and significantly with serum osteocal­ cin concentrations obtained by radioimmunoassay for women. M en had significantly higher total alkaline phosphatase and bone AP than women, w hereas liver AP concentrations did not differ betw een the two groups. Bone AP correlated negatively and significantly with age in m en, b u t not women. Osteocalcin concentrations tended to be higher in m en, b u t not