Effects of calcitonin and parathyroid hormone on the distribution of F-actin in the clear zone of osteoclasts in vivo.
To elucidate the relation between the distribution of F-actin bands in the clear zone and the bone-resorbing activity of osteoclasts in vivo, the endocranial surfaces of calvariae from 7-day-old Wistar rats were stained with F-actin-specific fluorescein isothiocyanate-labeled phalloidin (FITC-phalloidin) with and without the intraperitoneal injection of the calcium-regulating hormones, calcitonin (CT), and parathyroid hormone (PTH). Some specimens were double-stained with FITC-phalloidin and a monoclonal antibody, ED1, which stained monocytes and macrophages. In normal rats, almost 80% of the osteoclasts showed ring-shaped F-actin bands in the clear zone, and the remaining 20% showed arch- or line-shaped F-actin bands. From 15 min to 1 h after the injection of CT (salmon, 10 mg/kg), the number of osteoclasts with ring-shaped F-actin bands decreased significantly. At 1 h, few F-actin bands were detected in osteoclasts, which were still stained by ED1. However, these F-actin bands recovered to the normal level at 6 h. On the other hand, from 15 min to 6 h after the injection of PTH (bovine, 50 mg/kg), the number of osteoclasts with arch- or line-shaped F-actin bands decreased significantly. These results indicate that osteoclasts with arch- or line-shaped F-actin bands in the clear zone had lower bone-resorbing activity than those with ring-shaped F-actin bands, and that the formation of bands could be controlled by calcium-regulating hormones over the course of a few hours. Observation of the endocranial surfaces of calvariae might be useful for examining factors which affect the activities of osteoclasts in vivo.
Kuroda
H
H
Department of Pediatric Dentistry, School of Dentistry, Tohoku University, Sendai, Japan.
Nakamura
M
M
Kamiyama
K
K
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001862:Bone Resorption / Q000378:metabolism*; D002116:Calcitonin / Q000494:pharmacology*; D005452:Fluoresceins / Q000378:metabolism; D007274:Injections, Intraperitoneal; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010590:Phalloidine / Q000031:analogs & derivatives / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar
D000199:Actins; D005452:Fluoresceins; D010281:Parathyroid Hormone; C037191:fluorescein isothiocyanate-phalloidin; D010590:Phalloidine; D002116:Calcitonin