Postnatal expression of calretinin-immunoreactivity in periodontal Ruffini endings in the rat incisor: a comparison with protein gene product 9.5 (PGP 9.5)-immunoreactivity.
The postnatal expression of immunoreactivity for calretinin, one of the calcium binding proteins, and for protein gene product 9.5 (PGP 9.5), a general neuronal marker, was investigated in mechanoreceptive Ruffini endings in the periodontal ligament of the rat incisor. Age-related changes in the expression of these two proteins in periodontal nerves were further quantified with a computerized image analysis. At 1 day after birth, a few PGP 9.5-immunoreactive nerve fibers and a still smaller number of calretinin-positive fibers were found in the periodontal ligament: they were thin and beaded in appearance and no specialized nerve terminals were recognized. Tree-like terminals, reminiscent of immature Ruffini endings, were recognizable in 4-day-old rats by PGP 9.5-immunohistochemistry, while calretinin-immunostaining failed to reveal these specialized endings. At postnatal 7-11 days when PGP 9.5-immunostaining could demonstrate typical Ruffini endings, calretinin-immunopositive nerve fibers merely tapered off without forming the Ruffini type endings. A small number of Ruffini endings showing calretinin-immunoreactivity began to occur in the periodontal ligament at 24-26 days after birth when the occlusion of the first molars had been established. At the functional occlusion stage (60-80 days after birth), the Ruffini endings showing calretinin-immunoreactivity drastically increased in number and density, but less so than those positive for PGP 9.5-immunoreaction. The delayed expression of calretinin suggests that the function of the periodontal Ruffini endings is established after the completion of terminal formation because Ca2+, which binds to calcium binding proteins including calretinin with high affinity, plays an important role in mechano-electric transduction.
Asahito
T
T
Department of Oral Anatomy, Niigata University School of Dentistry, Japan.
Ohshima
H
H
Hanada
K
K
Wakisaka
S
S
Maeda
T
T
D000367:Age Factors; D000818:Animals; D064032:Calbindin 2; D007150:Immunohistochemistry; D007180:Incisor / Q000033:anatomy & histology* / Q000276:immunology / Q000502:physiology; D008465:Mechanoreceptors / Q000196:embryology* / Q000276:immunology / Q000378:metabolism*; D010513:Periodontal Ligament / Q000196:embryology* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D064030:S100 Calcium Binding Protein G / Q000276:immunology / Q000378:metabolism*; D013869:Thiolester Hydrolases / Q000276:immunology / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase
C576512:Calb2 protein, rat; D064032:Calbindin 2; D064030:S100 Calcium Binding Protein G; D013869:Thiolester Hydrolases; D043222:Ubiquitin Thiolesterase