Conjunctive effects of fibroblast growth factor and glycosaminoglycan on bone metabolism in neonatal Bartter Syndrome

The calciotropic activity of urine from a subject with neonatal Bartter syn drome (NBS) has been partially purified using ion-exchange and gel chromato graphic techniques. A bioassay using bone disks from rat calvaria was used to estimate calciotropic activity, which in the urine of the subject with N BS appears to be due to basic fibroblast growth factor (bFGF) bound to a gl ycosaminoglycan susceptible to heparitinase digestion. The calciotropic act ivity is eluted from DEAE-Sephacel and Sepharose CL-6B in a narrow band in association with metachromatic material and is destroyed by heparitinase an d blocked by an antibody to bFGF. After treatment of purified preparations with heparitinase, a component that is inactive alone bur develops calciotr opic activity in association with heparin can be isolated by affinity chrom atography on heparin-Sepharose columns. This component is recovered from th e column at NaCl concentrations expected to elute bFGF and is inactivated b y antibodies to bFGF. No calciotropic activity can be shown in glycosaminog lycan-containing fractions from urine from a normal boy or a normal man, bu t such fractions exhibit calciotropic activity if bFGF is added to the assa y system. When bFGF is added to urine from either normal subject followed b y ion-exchange chromatography on DEAE-Sephacel, calciotropic activity is el uted at NaCl concentrations closely similar to those found to elute calciot ropic activity from the urine of the NBS subject. It appears that the abnor mal findings in NBS urine are due to excess bFGF, although they could be du e to some abnormality of the glycosaminoglycan component.