Kp. May et al., THE EFFECT OF LOW-DOSE METHOTREXATE ON BONE METABOLISM AND HISTOMORPHOMETRY IN RATS, Arthritis and rheumatism, 37(2), 1994, pp. 201-206
Objective. To ascertain the effects of low-dose methotrexate (MTX) on
bone metabolism and histomorphometry in rats. Methods. Female Sprague-
Dawley rats (6 months old, n = 42) were divided into the following 4 g
roups: intraperitoneal (IF) injections of MTX, with and without ovarie
ctomy, and IP saline (controls), with and without ovariectomy. Injecti
ons were given for 16 weeks. The MTX dose was equivalent to a standard
dose for rheumatoid arthritis in humans that would yield similar seru
m MTX levels (0.6 +/- 0.1 mu moles). Results, Bone formation (assessed
by serum alkaline phosphatase and osteocalcin levels and histomorphom
etry) was significantly lower in the MTX groups, and bone resorption (
assessed by urinary hydroxyproline levels and histomorphometry) was in
creased in the MTX groups. Bone mass was significantly diminished in t
he MTX groups. Conclusion. Prolonged administration of low-dose MTX in
rats causes significant osteopenia via suppression of osteoblast acti
vity and stimulation of osteoclast recruitment, which results in incre
ased bone resorption.