title: L-type calcium channels in growth plate chondrocytes participate in endochondral ossification.
abstract: Longitudinal bone growth occurs by a process called endochondral ossification that includes chondrocyte proliferation, differentiation, and apoptosis. Recent studies have suggested a regulatory role for intracellular Ca(2+) (Ca(i) (2+)) in this process. Indirect studies, using Ca(2+) channel blockers and measurement of Ca(i) (2+), have provided evidence for the existence of Ca(2+) channels in growth plate chondrocytes. Furthermore, voltage-gated Ca(2+) channels (VGCC), and specifically L- and T-type VGCCs, have been recently described in murine embryonic growth plates. Our aim was to assess the effect of L-type Ca(2+) channel blockers on endochondral ossification in an organ culture. We used cultures of fetal rat metatarsal rudiments at 20 days post gestational age, with the addition of the L-type Ca(2+) channel blockers verapamil (10-100 microM) or diltiazem (10-200 microM) to the culture medium. Longitudinal bone growth, chondrocyte differentiation (number of hypertrophic chondrocytes), and cell proliferation (incorporation of tritiated thymidine) were measured. Verapamil dose-dependently decreased growth, the number of hypertrophic chondrocytes, and cell proliferation, at concentrations of 10-100 microM. Growth and the number of hypertrophic chondrocytes decreased significantly with diltiazem at 50-100 microM, and proliferation decreased significantly at concentrations of 10-200 microM. Additionally, there was no increase in apoptosis over physiological levels with either drug. We confirmed the presence of L-type VGCCs in rat rudiments using immunohistochemistry, and showed that the antagonists did not alter the pattern of VGCC expression. In conclusion, our data suggest that L-type Ca(2+) channel activity in growth plate chondrocytes is necessary for normal longitudinal growth, participating in chondrocyte proliferation and differentiation.
authors.affiliation: Program of Pathophysiology, Faculty of Medicine, Institute of Biomedical Sciences, University of Chile, Santiago, Chile. emancill@med.uchile.cl
authors.forename: Edna E
authors.initials: EE
authors.lastname: Mancilla
authors.forename: Mario
authors.initials: M
authors.lastname: Galindo
authors.forename: Barbara
authors.initials: B
authors.lastname: Fertilio
authors.forename: Mario
authors.initials: M
authors.lastname: Herrera
authors.forename: Karime
authors.initials: K
authors.lastname: Salas
authors.forename: Hector
authors.initials: H
authors.lastname: Gatica
authors.forename: Annelise
authors.initials: A
authors.lastname: Goecke
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004110:Diltiazem / Q000494:pharmacology; D006132:Growth Plate / Q000166:cytology*; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D014700:Verapamil; D004110:Diltiazem