, . r .1~ 4
Annotation A Potential for High Collagen Turnover in the Molar Pulp Independent of Eruption WALTER A. ORLOWSKI
Department of Pathology, School of Dentistry, Fairleigh Dickinrson University, 110 Fuller Place, Hackensack, N. Y. 07601, USA J Dent Res 56(12): 1488, December 1977. Our earlier studies (ORLOWSKI and DOYLE, Arch Oral Biol 21:391, 1976) have shown that incorporation of H3-proline was not only high into the collagen of rat incisor pulp but also into molar tooth pulp. Subse-
quently (ORLOWSKI,J Dent Res 56:437, 1977), turnover of collagen in incisor pulp was found to be higher than would be expected on the basis of eruption with a half life (T1i) for the label disappearance being 6.0 days (based on . decrease of specific activity of hydroxyproline with time). This report gives results obtained for collagen turnover in rat molar pulps used in the previous study (1977) for the determination of turnover rates in pulps of erupting incisors. The purpose was to determine the extent to which the high metabolic activity observed in the incisor pulp was the result of eruption and whether there was significant metabolic activity indep)endent of eruption. Me thodology and calculations can be found in the previ ous study (1977). Five groups of 6 rats each were used; ,each rat received 0.7 1tCi of H3-5-proline (AmershaLm-Searle, Il.) per gram of body weight, intraperit(oneally. A group of rats was sacrificed 2, 4, 8, 12, and Il8 days postinjection. Jaws were collected and lyophil Lized; pulps from maxillary and mandibular molars Mvere collected and pooled for each group. Duplicate .analyses were done on each pooled sample. Proline ;and hydroxyproline were separated by ion-exRece-ived for publication July 18, 1977. Accezpted
for publication November 4, 1977.
SPEECIFIC ACTIVITY OF HYDROXYPROLINE k 20
0
I-NCISORS
ao
0
-J (n
07 (
5 0-
-J I-
0)
0
>~
0s 0
\0 \ 0_
0-
0 I-
2
4
8 12 TI ME (DAYS)
18
Fig. - A semi-log plot of the change in specific activity of hydroxKyproline and proline in incisor and molar pulps.
TABLE CHANGE IN TRITIUM ACTIVITY IN MOLAR PULP
Days
2
8
12
18
Specific Specific in Activity Activity Collagent OH-Prolinet Prolinet 7o Activity
Whole* Tissue
4094
2997 2107
1150 1012
15.8 16.0 22.8 30.7 33.4
32.9
25.9 24.6
17.0 15.7
104.0 66.7 43.6 22.7 19.6
*Expressed in DPM/mg of dry weight of tissue. tCalculated by multiplying activity in hydroxyproline (dpm/mg) by 2.15. The product is then divided by total activity (in dpm/mg) and multiplied by 100. tExpressed in DPM/.ig of the amino acid. change chromatography and specific activities determined. The amount of collagen, expressed in terms of dry weight, averaged around 7%. Total activity, expressed in dpm/mg, decreased rapidly over the 18day period (table). Most decrease was due to loss of activity from noncollagenous components, represented by decrease in specific activity from proline, 84% to 66.6% of which was present in noncollagenous components. Collagen was more stable; but there was a gradual decrease of activity in collagen -less than half remained after 18 days. In the figure, the disappearance of label from hydroxyproline in molar pulps, as determined here, was compared to the loss of activity from incisor pulp determined previously (1977). The T4A estimated from the slopes of the curves was 13.5 days in the molar pulp (turnover time, 19.0 days). The Tl½ for the incisor pulp was 6.0 days. As would be expected there was more active remodeling of pulpal collagen in erupting teeth. However, remodeling in molar pulp, although slower, was nevertheless quite rapid and probably independent of eruption. The turnover reported in this study represented the most active metabolic pool in the pulp. Our study was essentially designed to identify such active pool and does not preclude the existence of a stable pool. In our dissecting techniques, the predentin and dentin were not included and thus the turnover reported here probably was unrelated to the synthesis of predentin. It most likely represented the turnover of the collagen of the pulp matrix. The metabolism of collagen in molar pulps was slower than that of incisors; however, it was still fairly rapid (Tlh of 13.5 days). This suggests that dental pulp possesses an inherent potential for high metabolic activity independent of eruption. This investigation was supported by a USPHS Grant No. DE-04023 from the National Institute of Denial Research.
1488 Downloaded from jdr.sagepub.com at NORTH DAKOTA STATE UNIV LIB on May 19, 2015 For personal use only. No other uses without permission.
Annotation A Potential for High Collagen Turnover in the Molar Pulp Independent of Eruption WALTER A. ORLOWSKI
Department of Pathology, School of Dentistry, Fairleigh Dickinrson University, 110 Fuller Place, Hackensack, N. Y. 07601, USA J Dent Res 56(12): 1488, December 1977. Our earlier studies (ORLOWSKI and DOYLE, Arch Oral Biol 21:391, 1976) have shown that incorporation of H3-proline was not only high into the collagen of rat incisor pulp but also into molar tooth pulp. Subse-
quently (ORLOWSKI,J Dent Res 56:437, 1977), turnover of collagen in incisor pulp was found to be higher than would be expected on the basis of eruption with a half life (T1i) for the label disappearance being 6.0 days (based on . decrease of specific activity of hydroxyproline with time). This report gives results obtained for collagen turnover in rat molar pulps used in the previous study (1977) for the determination of turnover rates in pulps of erupting incisors. The purpose was to determine the extent to which the high metabolic activity observed in the incisor pulp was the result of eruption and whether there was significant metabolic activity indep)endent of eruption. Me thodology and calculations can be found in the previ ous study (1977). Five groups of 6 rats each were used; ,each rat received 0.7 1tCi of H3-5-proline (AmershaLm-Searle, Il.) per gram of body weight, intraperit(oneally. A group of rats was sacrificed 2, 4, 8, 12, and Il8 days postinjection. Jaws were collected and lyophil Lized; pulps from maxillary and mandibular molars Mvere collected and pooled for each group. Duplicate .analyses were done on each pooled sample. Proline ;and hydroxyproline were separated by ion-exRece-ived for publication July 18, 1977. Accezpted
for publication November 4, 1977.
SPEECIFIC ACTIVITY OF HYDROXYPROLINE k 20
0
I-NCISORS
ao
0
-J (n
07 (
5 0-
-J I-
0)
0
>~
0s 0
\0 \ 0_
0-
0 I-
2
4
8 12 TI ME (DAYS)
18
Fig. - A semi-log plot of the change in specific activity of hydroxKyproline and proline in incisor and molar pulps.
TABLE CHANGE IN TRITIUM ACTIVITY IN MOLAR PULP
Days
2
8
12
18
Specific Specific in Activity Activity Collagent OH-Prolinet Prolinet 7o Activity
Whole* Tissue
4094
2997 2107
1150 1012
15.8 16.0 22.8 30.7 33.4
32.9
25.9 24.6
17.0 15.7
104.0 66.7 43.6 22.7 19.6
*Expressed in DPM/mg of dry weight of tissue. tCalculated by multiplying activity in hydroxyproline (dpm/mg) by 2.15. The product is then divided by total activity (in dpm/mg) and multiplied by 100. tExpressed in DPM/.ig of the amino acid. change chromatography and specific activities determined. The amount of collagen, expressed in terms of dry weight, averaged around 7%. Total activity, expressed in dpm/mg, decreased rapidly over the 18day period (table). Most decrease was due to loss of activity from noncollagenous components, represented by decrease in specific activity from proline, 84% to 66.6% of which was present in noncollagenous components. Collagen was more stable; but there was a gradual decrease of activity in collagen -less than half remained after 18 days. In the figure, the disappearance of label from hydroxyproline in molar pulps, as determined here, was compared to the loss of activity from incisor pulp determined previously (1977). The T4A estimated from the slopes of the curves was 13.5 days in the molar pulp (turnover time, 19.0 days). The Tl½ for the incisor pulp was 6.0 days. As would be expected there was more active remodeling of pulpal collagen in erupting teeth. However, remodeling in molar pulp, although slower, was nevertheless quite rapid and probably independent of eruption. The turnover reported in this study represented the most active metabolic pool in the pulp. Our study was essentially designed to identify such active pool and does not preclude the existence of a stable pool. In our dissecting techniques, the predentin and dentin were not included and thus the turnover reported here probably was unrelated to the synthesis of predentin. It most likely represented the turnover of the collagen of the pulp matrix. The metabolism of collagen in molar pulps was slower than that of incisors; however, it was still fairly rapid (Tlh of 13.5 days). This suggests that dental pulp possesses an inherent potential for high metabolic activity independent of eruption. This investigation was supported by a USPHS Grant No. DE-04023 from the National Institute of Denial Research.
1488 Downloaded from jdr.sagepub.com at NORTH DAKOTA STATE UNIV LIB on May 19, 2015 For personal use only. No other uses without permission.
