Improved method for quantitative determination in serum of alkaline phosphatase of skeletal origin

In this quantitative method for detection of skeletal alkaline phosphatase (EC 3.1.3.1) activity in human serum, intestinal and placental alkaline phosphatase activities are recognized by their susceptibility to inhibition by L-phenylalanine, and skeletal and hepatic alkaline phosphatases are distinguished by their different sensitivities to inactivation by heat. Alkaline phosphatase isoenzymes prepared from organ sources may behave differently from the corresponding isoenzymes in serum. Our procedure allows us to include organ-derived internal standards of skeletal, intestinal, and biliary alkaline phosphatase to minimize between-assay variation. In preliminary applications, we have found that (a) total serum alkaline phosphatase activity is extremely variable in post-menopausal osteoporotic subjects and is not a reliable index of skeletal alkaline phosphatase activity; (b) seven osteoporotic patients responding to therapy with sodium fluoride with increased bone formation showed increased skeletal alkaline phosphatase activity in their serum as compared with age-matched controls (p less than 0.005); and (c) 10 post-menopausal osteoporotic patients responding to therapy with stanozolol with increased total body calcium showed an increase in circulating skeletal alkaline phosphatase activity (p less than 0.001).

Assessment of 25-hydroxyvitamin D 1 alpha-hydroxylase reserve in postmenopausal osteoporosis by administration of parathyroid extract

Previous studies have shown that the mean serum concentration of 1,25-dihydroxyvitamin D [1,25-(OH)2D] is lower than normal in patients with postmenopausal osteoporosis. We studied the mechanism of this abnormality in 12 women with postmenopausal osteoporosis and 10 age-comparable normal women. Parathyroid extract (200 U, twice daily for 3 days) was administered to stimulate the enzymatic conversion of 25-hydroxyvitamin D (25OHD) to 1,25-(OH)2D. The serum concentration of 1,25-(OH)2D was lower (P less than 0.05) at a baseline determination in the osteoporotic subjects than in the normal women and increased significantly (P less than 0.001) above basal values after the administration of parathyroid extract in both groups; however, the degrees of increase in the control and osteoporotic subjects were similar. We conclude, at least under the conditions of our study, that 25OHD 1 alpha-hydroxylase is normally responsive to parathyroid hormone in postmenopausal osteoporosis. Thus, the apparently impaired metabolism of 25OHD to 1,25-(OH)2D appears to be secondary to a decrease in factors that abnormally stimulate 25OHD 1 alpha-hydroxylase activity rather than a primary defect in enzyme reserve capacity.

Relationship of the activity of the bone isoenzyme of serum alkaline phosphatase to urinary hydroxyproline excretion in metabolic and neoplastic bone diseases

A significant correlation between the activity of the bone isoenzyme or serum alkaline phosphatase and the urinary hydroxyproline excretion in osteomalacia, osteoporosis, primary hyperparathyroidism with osteodystrophy, Paget's disease, secondary bone tumours, and in a control group was found (P less than 0.001). This close correlation was not observed between these variables in patients with active acromegaly. Diagnosis determined from these indices of formation and turnover of bone matrix agreed with that established by histological and histochemical examination of bone, by X-ray investigation of the skeleton, and by the radionuclear 85Sr test. The relationship between the activity of bone isoenzyme and urinary hydroxyproline excretion differed in metabolic bone diseases with a high bone turnover, in patients with osteoporosis and in patients with early osteoclastic bone metastases.

Short-term effects of varying doses of 1 alpha-hydroxyvitamin D3 on blood and urine chemistry and calcium absorption of osteoporotic patients

During a period of 4-7 days, synthetic 1 alpha-hydroxyvitamin D3 (1alpha-OH-D3) was given to osteoporotic patients with hip fractures in 3 different dose levels, viz. 1 microgram, 2 microgram, and 4 microgram, in combination with calcium. The increase in serum calcium level was more prominent during treatment with 2 microgram and 4 microgram doses of 1 alpha-OH-D3 and was also dependent on the duration of treatment. The level of serum phosphate was only slightly elevated. The urinary calcium excretion increased, while the urine phosphate and hydroxyproline excretion decreased. The intestinal absorption of calcium increased in rate during treatment with 1 alpha-OH-D3. On discontinuation of treatment, values did not normalize within 6 days. The administration of small doses of 1 alpha-OH-D3 did not seem to expose osteoporotic patients to the risks of hypercalcemia. The efficiency of vitamin D metabolites in the treatment of osteoporosis requires further investigation.

[Gamma-glutamyltranspeptidase in chronic polyarthritis. I. Comparison with a control group and relationship with alkaline phosphatase]

Gamma-GT, alcaline phosphatase and other parameters of abnormal liver functions were estimated in 54 consecutive in-patients having active RA but without a previous history or clinical signs of liver disease, and compared with a matched control group, suffering from degenerative rheumatic disease. There was a slight to moderate elevation of gamma-GT in 40.4% of the RA-patients (mean value 27.2 IU/l) and in 32.1% (mean value 22.3 IU/l) of the control group, respectively. The difference was not significant. Abnormal values in the control group occurred mainly in patients with peri-arthropathia of the shoulder, before mobilisation under anaethetic (3 of 5) and - coxarthrosis before total hip replacement (4 of 12). Alkaline phosphatase was elevated in 25.9% of the RA-patients (mean value 41.3 +/- 21.9 IU/l) and in 14.8% of the control group (mean value 34.3 +/- 15.9 IU/l). The difference was significant. There was a correlation between gamma-GT and alcaline phosphatase in the RA-group (r = 0.549, p less than 0.001) but not in the control group (r = 0.102). Abnormal values found in the control group were mainly found among patients with osteoporosis, following fractures, and coxarthrosis. The frequency of abnormal results and the value of the means increased with raising disease activity. Two groups of 30 and 32 patients, respectively, were examined at intervals of 2 or 4 weeks over a period of 6-10 and 18 months, respectively, and showed temporary elevations os gamma-GT in 3/4 of all patients, of GOT in 2/3 of alcaline phosphatase in 1/2 and of GPT in 1/3. Compared with other parameters of liver disease gamma-GT did not react in a different but in a more sensitive way. In our opinion it is the most sensitive indicator of reactive changes of the liver in RA.

The clinical significance of serum alkaline phosphatase isoenzymes in locomotor diseases

AP isoenzymes were estimated in 292 patients with locomotor diseases and in 124 healthy controls. The diagnostic usefulness of AP determination is increased by estimation of isoenzymes. Investigations were made to study the biological profile of organ specific AP activities: 1. Rheumatoid arthritis and Reiter's syndrome - the total AP and L-AP activities were increased. 2. Ankylosing spondylitis treated by physiotherapy - the total AP, B-AP and I-AP activities were increased. After drug therapy an increase occurred also in L-AP activity while I-AP activity showed no significant change. 3. Progressive OA of hip and knee showed increased levels of total AP and B-AP activities. 4. Degenerative diseases of the spine, chiefly cases of discopathy, showed significantly reduced levels of AP and B-AP activities. 5. In osteoporosis there was an increase in total AP, L-AP, B-AP and I-AP activities. 6. In the active generalised form of Paget's disease, increased levels were found of total AP, B-AP, I-AP and L-AP activities. 7. In neoplastic diseases the isoenzymes can help to reveal metastatic dissemination and thus aid preoperative evaluation. 8. In gout and hyperuricemic syndromes there was a relative increase of B-AP activity and non-significant fall of L-AP activity. Increased levels of L-AP occured in patients with gallbladder disease, after immunosuppressive therapy or after infectious hepatitis. A fall of L-AP levels was found after Corticotrophin and after intraarticular administration of Kenalog. Increased B-AP activities occurred after total hip replacement, in acute or chronic pyelonephritis and in active osteonecrosis and osteoporosis. Anabolic therapy caused a significant fale of B-AP activity to fall significantly. Reduced B-AP levels were also found after antibiotic therapy. Increased I-AP activity was found in cases of osteoporosis, and in secondary amyloidosis; reduced I-AP activity was seen in mucous colitis. The activity of I-AP is assumed to increase as a result of the changed intestinal calcium and phosphorus regulation occurring in association with the enhanced bone tissue metabolism. From this point of view an order of significance is given for the activity of bone pathology in the separate diagnostic groups of locomotor diseases.

Effect of sex hormones on bone in primary osteoporosis

The effect of sex hormones on bone tissue was studied in 12 osteoporotic patients. Surfaces of bone undergoing formation and resorption were determined by quantitative microradiography of iliac crest biopsy samples before and after treatment with estrogens in 11 postmenopausal women and with testosterone in one gonadally competent man. Before treatment, bone resorption was greater than normal in all but one patient and bone formation was normal. After treatment, bone resorption decreased to within the normal range in all patients, and bone formation did not change significantly. Biochemical studies showed significant decreases in serum calcium, phosphorus, and alkaline phosphatase levels and in urinary excretion of calcium and hydroxyproline. These changes are believed to be the consequence of the effect of the hormones on bone. The data indicate that the major effect of sex hormones in osteoporosis is an inhibition of bone resorption.