High predictivity of galactosyl-hydroxylysine in urine as an indicator of bone metastases from breast cancer.

We measured the urinary excretion of galactosyl-hydroxylysine (GH) and hydroxyproline in two groups of women with breast cancer, with (M+, n = 24) and without (Mo, n = 30) clinical, scintigraphic, or radiological evidence of bone metastases. Both these compounds are excreted in larger amounts in the M+ group than in the Mo patients. However, GH, which is a specific marker for bone collagen, provides better predictivity for bone metastases than does hydroxyproline: 92% sensitivity and 90% specificity vs 74% and 79%, respectively, for hydroxyproline.

High-performance liquid chromatographic preparation of galactosyl-hydroxylysine, a specific bone collagen marker.

Galactosyl-hydroxylysine, a specific bone collagen marker, has been prepared directly from human urine samples by high-performance liquid chromatography (HPLC) on a preparative column. The compound is the didansyl derivative, as proved by HPLC and mass spectrometry under fast atom bombardment conditions. Since this compound is not commercially available, the procedure reported appears to be the simplest way to prepare it, which is necessary to measure the urinary excretion of this collagen metabolite by HPLC.

Urinary beta-1-galactosyl-0-hydroxylysine (GH) as a marker of collagen turnover of bone.

beta-1-galactosyl-0-hydroxylysine (GH) was measured in the urine of 59 women and 48 men, aged 30-79 years, by High Performance Liquid Chromatography (HPLC) of the dansylated derivative. Vertebral mineral density, measured by quantitative computed tomography (QCT), and urinary GH were inversely correlated (r = -0.74; P less than 0.001). High rate of bone mineral loss is associated with a high urinary GH excretion. Measurement of GH in urine provides a simple and noninvasive method for the evaluation of the extent of bone resorption in large groups of subjects and appears to be more specific than urinary hydroxyproline excretion.

Determination of galactosyl hydroxylysine in urine as a means for the identification of osteoporotic women.

A sensitive and specific method is proposed to follow bone collagen degradation. The procedure consists of the measurement of galactosyl hydroxylysine (GH) in urine by HPLC. The aim of the work is to assess the predictive values of the method for the identification of post-menopausal osteoporotic women. By assuming the value of 12 mumol/g creatinine as the threshold value, the sensitivity of the test is 87% and the specificity 60%. Individuals with a GH/creatinine ratio of 12 or below are not likely to be at risk of bone fractures: an equivalent predictive value is provided by the measurement of bone density by quantitative computed tomography. This biochemical method is however simple and not invasive and may be frequently repeated.

Biochemical and immunohistochemical evidence that in cartilage an alkaline phosphatase is a Ca2+-binding glycoprotein.

A glycoprotein that exhibits alkaline phosphatase activity and binds Ca2+ with high affinity has been extracted and purified from cartilage matrix vesicles by fast protein liquid chromatography. Antibodies against this glycoprotein were used to analyze its distribution in chondrocytes and in the matrix of calcifying cartilage. Under the light microscope, using immunoperoxidase or immunofluorescence techniques, the glycoprotein is localized in chondrocytes of the resting zone. At this level, the extracellular matrix does not show any reaction. In the cartilage plate, between the proliferating and the hypertrophic region, a weak immune reactivity is seen in the cytoplasm, whereas in the intercolumnar matrix the collagen fibers appear clearly stained. Stained granular structures, distributed with a pattern similar to that of matrix vesicles, are also visible. Calcified matrix is the most stained area. These results were confirmed under the electron microscope using both immunoperoxidase and protein A-gold techniques. In parallel studies, enzyme activity was also analyzed by histochemical methods. Whereas resting cartilage, the intercellular matrix of the resting zone, and calcified matrix do not exhibit any enzyme activity, the zones of maturing and hypertrophic chondrocytes are highly reactive. Some weak reactivity is also shown by chondrocytes of the resting zone. The observation that this glycoprotein (which binds Ca2+ and has alkaline phosphatase activity) is synthesized in chondrocytes and is exported to the extracellular matrix at the time when calcification begins, suggests that it plays a specific role in the process of calcification.