The effect of phenytoin on collagenase and gelatinase activities in UMR 106-01 rat osteoblastic osteosarcoma cells.
Phenytoin (PHT), a widely used anticonvulsant, has been shown to inhibit bone resorption in rodent organ cultures. The drug also has complex effects on bone metabolism including chronic clinical symptoms of osteomalacia. However, the precise mechanism of PHT action in bone is still unclear. Neutral collagenases that specifically cleave native collagen have been implicated in the turnover of connective tissue. The effect of PHT was assessed on collagenase and gelatinase activities from UMR 106-01 rat osteoblastic osteosarcoma cells. Semiconfluent cells were treated with PHT (50 and 10 micrograms/ml) in the presence of bovine parathyroid hormone, b-PTH-(1-34), at 10(-7) M for 24, 48, 72 and 96 h. The media were assayed following concentration, APMA activation, and incubation with native or denatured [3H]-methyl collagen substrate (approximately 100,000 dpm) at 27 degrees C for 18 h and 35 degrees C for 2 h, respectively. Enzyme activities were presented as primary counts per minute for each time point and calculated as % activity of PTH at 10(-7) M. Parathyroid hormone (10(-7) M) stimulated collagenase activity (approximately 65-fold) and gelatinase activity (approximately 400-fold). PHT (50 micrograms/ml) reduced the PTH-stimulated collagenase activity by 18-53% and the gelatinase activity by 58-72%. SDS PAGE and fluorography following PHT treatment indicated a PHT-induced partial inhibition of PTH-stimulated degradation to alpha A chains of Type I collagen. Phenytoin may inhibit bone resorption through its action on the transcription, synthesis, and/or secretion of the collagenolytic enzymes, collagenase and gelatinase.
Vernillo
A T
AT
Department of Oral Medicine and Pathology, New York University College of Dentistry, NY 10010.
Ramamurthy
N S
NS
Lee
H M
HM
Rifkin
B R
BR
D000818:Animals; D001859:Bone Neoplasms / Q000201:enzymology*; D018093:Gelatinases; D003012:Microbial Collagenase / Q000378:metabolism*; D012516:Osteosarcoma / Q000201:enzymology*; D010434:Pepsin A / Q000378:metabolism*; D010672:Phenytoin / Q000494:pharmacology*; D051381:Rats; D014407:Tumor Cells, Cultured
D010672:Phenytoin; D010434:Pepsin A; D018093:Gelatinases; D003012:Microbial Collagenase