Citrate in mineralized tissues—VII The effects of rehabilitation with phosphate or with phosphate and vitamin D in rats previously maintained on diets deficient in both

In each of two experiments fifty weanling rats were maintained on diets low in phosphorus and vitamin D for 7 weeks. Ten animals in each experiment were then killed. In Experiment 1 the remaining forty rats were transferred to a diet containing adequate phosphorus and vitamin D; in Experiment 2 the animals were transferred to a diet adequate in phosphorus but still low in vitamin D. In both experiments animals were killed at intervals during the 35-day period following transfer and the concentrations of calcium, inorganic phosphate and citrate in blood and bone were determined.

When the animals were transferred to a diet adequate in phosphorus but with no added vitamin D (Experiment 2) the serum citric acid concentration fell from its initially high level to a minimum value after 16 days and then rose slightly at 35 days. The bone citric acid concentration subsided during the 35-day period.

When the animals were transferred to a diet containing adequate phosphorus and vitamin D (Experiment 1) the high serum citric acid concentration again declined after 35 days, but with the difference that there was a peak value of 16 days. There was a sharp increase in bone citric acid concentration followed by a steady decline to normal after 35 days.

These differences in reaction in the two experiments support the view that vitamin D has a direct action on citric acid synthesis in bone but that not all bone citric acid is formed in situ.     

Variation in sialic acid concentration in gingival tissue from rats receiving excess vitamin A

The effect of 1 to 5 doses of 15,000 I.U. of vitamin A on N-acetyl neuraminic acid (NANA) concentration in gingival tissue from rats was studied. Increased sialic acid concentration was observed in those animals receiving up to 4 doses of the vitamin, while a decreased concentration was found in the 5 doses group. Also examined was the interrelationship between vitamin A-cortisol and vitamin A-ascorbic acid. The profile of NANA variation in the groups receiving vitamin A plus ascorbic acid was similar to that of animals receiving only ascorbic acid. The data obtained for the groups receiving both vitamin A and cortisol, did not differ from that obtained for the groups receiving only vitamin A.     

Effects of dietary restriction on the composition of lipids in rat teeth

The effect of food restriction on the quality and quantity of lipids in the teeth of rats was studied. Control animals were fed a nutritionally adequate diet ad libitum while test animals were restricted to 65 per cent as much diet day by day. Both groups were started on the regimen at weaning. Approximately half were sacrificed at 43 days of age. and the remainder at 78 days of age. Compared to control group, the rats fed the restricted diet gained less body weight and retained less lipids in teeth. The tooth lipids of test animals were predominantly phospholipids and cholesterol, while those of control animals were mostly triglycerides and phospholipids. Palmitic, stearic and oleic acids were the major fatty acids in the teeth of rats of both groups. The ratio of oleic acid to total fatty acids in teeth was higher in the test animals than in the control animals, and it increased sharply in the teeth of control animals as they advanced from 43 to 78 days of age. However, the fatty acid composition of tooth lipids of test animals did not change significantly during this period. Thus, food restriction can affect the lipid composition of the teeth of rats. The structural lipids (phospholipids and cholesterol) are retained while the storage lipids (triglycerides) are reduced.     

Flow rate,amylase activity,and protein and sialic acid concentrations of saliva from children aged 18, 30 and 42 months attending a baby clinic

Whole-saliva samples were collected under slight suction from children enrolled in a dental-care programme at a baby clinic and analysed according to sex. The children were allocated to three age groups: 18, 30 and 42 months. No distinct sex difference was found for flow rate; there was a statistically non-significant tendency for an increased rate in females. In the males the flow rates of the 30- and 42-month groups were higher than those of the 18-month group; a similar result was obtained when findings for both sexes were combined. There was no difference in salivary protein concentration between the sexes or the age groups. Amylase activity increased significantly in males from 18 to 30 months of age. Sialic acid concentration (micromol/mg protein) showed a sex difference for the 18-month group; it was 38% higher in males than in females, and 48% higher than in the males of 42 months. This trend toward a reduction in sialic acid concentration with age suggests a reduced synthesis and secretion of glycoproteins.     

Effects of zinc deficiency on developmental changes in alkaline phosphatase and carbonic anhydrase activities in the submandibular gland of the rat

The alkaline phosphatase (AP) and carbonic anhydrase (CA) activities were studied in male rats placed at weanling age on a diet containing 0.4 parts/10⁶ of zinc for periods of 9, 18 and 27 days. Weight-matched pair-fed rats were kept on the same diet supplemented with 40 parts/10⁶ of zinc. The body weight of controls showed a continuous increase; body weight of zinc-deficient animals remained unchanged. Zinc concentration in submandibular gland was the same in all groups of control and zinc-deficient animals. AP activity, chiefly localized in the myoepithelial cells, progressively increased in controls from day 9 to 27. AP activity in the zinc-deficient animals did not increase. It was lower than in controls even at 9 days and further decreased with prolonged zinc deficiency. CA activity, chiefly localized in cells of the duct system, rose with age in the controls at twice the rate of AP activity, a rise attributed to the steep rise in proportion of duct cells reported for this age span. By contrast, CA activity in the glands of zinc-deficient rats remained constant at all periods of deficiency, accounting for the increasing difference from controls with prolonged zinc deficiency. Failure of CA activity to rise with age in zinc-deficient rats is attributed to failing proliferation of duct cells, reflecting the inhibition of cell proliferation reported for many tissues of the zinc-deficient animals, a view supported by the maintenance of unchanged body weight over a 4-week-period. Inhibition studies using acetazolamide showed identical degress of inhibition in homogenates from control and deficient animals over a wide range of inhibitor concentrations. Rats fed for 9 days on the zinc-supplemented diet after 27 days on the deficient diet doubled their weight and showed AP and CA activities of the same level as controls that were pair-fed for 27 days and given unrestricted food for the last 9 days.     

Dose and age dependent variations in effect of tetracycline on enamel formation in rat

abstract — Incidence of rats with gross enamel lesions in response to tetracycline hydrochloride (TC) was studied in relationship to age, tooth type, and concentration of antibiotic in the injection fluid. Incidence was defined as percentage of animals with defects in at least one incisor or one molar. Serum levels were measured at various intervals in 4- and 75-day-old rats, which received a single i.p. injection with 130 mg/kg bw in concentrations of either 13 or 25 mg/ml saline. The study confirmed that the effect of TC on enamel varied with age of the animal and that the molar responded more readily than the incisor. Furthermore, the incidence was higher the higher the concentration of antibiotic. This effect appeared tied to a direct relationship between concentration and serum level. Serum levels declined more slowly in the younger than in the older rats, resulting in significantly higher levels 6, 24 and 48 h after dosing, which correlated with a more extensive labeling of the dentin in the young rats. The possible roles of serum levels, capillary supply and cell susceptibility are discussed in relation to differences in response with animal age, between tooth types, tooth surfaces and with age of the secretory cells.     

Effect of donor age on the concentrations of histatins in human parotid and submandibular/sublingual saliva

Histatins are small proteins of human glandular saliva that have antifungal properties. Recent studies show that oral candidal infections increase with age, suggesting an age-associated compromise in oral host defence. Here, the effect of age and of physiological gland stimulation on the concentration and secretion of salivary histatins was investigated. Parotid and submandibular/sublingual salivas were collected from six young adults under unstimulated, mechanical (chewing) and gustatory (0.025 M and 0.1 M citric acid) stimulation, and the concentration and secretion of histatins was measured by cationic polyacrylamide gel electrophoresis with subsequent densitometric scanning of the stained gels. With gland stimulation, parotid saliva showed no significant increase in histatin concentration (microg/ml); however, histatin secretion (microg/min) increased up to 26-fold (p<0.005; ANOVA). Stimulation of submandibular/sublingual saliva resulted in significant increases in both histatin concentration (p<0.005) and secretion (p<0.0005). Ageing effects on salivary histatins were determined in citric acid (0.1 M)-stimulated parotid and submandibular/sublingual saliva samples collected from 80 individuals (divided into four age groups having approximately equal numbers of males and females: 35-44 years; 45-54 years; 55-64 years and 65-76 years). None of the patients was taking medications or wore dentures. ANOVA showed no sex differences in histatins. Regression analysis showed significant age-associated decreases for parotid saliva histatin concentration (p<0.002) and secretion (p<0. 002) as well as for submandibular/sublingual saliva histatin concentration (p<0.0001) and secretion (p<0.0001). Both saliva types showed significant (p<0.0001) decreases in the histatin concentration per mg of total protein, suggesting a preferential decrease in salivary histatins compared to total salivary protein. These results suggest that the salivary histatin component of the oral host defence system is compromised with increasing age.     

Age changes in the rat temporomandibular joint articular disc: a biochemical study on glycosaminoglycan content

SUMMARY The temporomandibular joint (TMJ) articular discs were removed from female Sprague-Dawley rats 3, 5, 10, 32, 90 and 130 weeks of age. Glycosaminoglycans (GAGS) were extracted from the discs by heat treatment, alkali treatment and digestion with Pronase E, and purified by precipitation with cetylpyridinium chloride and ethanol. The concentration of total GAG was highest in the 3 week extracts and tended to decrease with age. Dermatan sulphate was the predominant GAG detected in all age groups along with chondroitin sulphate, hyaluronic acid and heparan sulphate. The disaccharides obtained from chondroitin sulphate were ΔDi-4S, ΔDi-6S and ΔDi-OS, with ADi-4S being the predominant isomer followed by ADi-6S for all ages of all the GAG examined. The concentration of chondroitin sulphate showed a decrease with age. Quantitative changes of GAG with age may be related to functional changes in TMJ discs.     

单侧磨牙缺失对大鼠海马神经递质含量的影响

目的:研究单侧磨牙缺失对大鼠脑部海马区主要神经递质含量的影响。方法:23只10月龄Wistar大鼠随机分为对照组和左侧磨牙拔除组,六周后,大鼠快速断头处死,分离海马区脑组织,拔牙组海马左右侧分开,分别测定氨基酸类和单胺类神经递质的含量。结果:①拔牙组左、右侧海马中g-氨基丁酸(GABA)和牛磺酸(Tau)含量与对照组比较均升高(P<0.05);②拔牙组左、右侧海马中5-羟吲哚乙酸(5-HIAA)含量、5-HIAA/5-HT比值与对照组比较均降低(P<0.001);③拔牙组大鼠左侧海马内谷氨酸(Glu)含量与对照组比较升高(P<0.05);④拔牙组大鼠右侧海马内去甲肾上腺素(NE)和5-羟色胺(5-HT)含量与对照组比较升高(P<0.05)。结论:单侧磨牙缺失后影响大鼠海马区氨基酸类和单胺类神经递质水平。     

Influence of selected fatty acids upon plaque formation and caries in the rat

Weanling rats were given high-sucrose cariogenic diets containing 2 per cent lauric acid, linoleic acid, nonanoic acid or monolaurin. Plaque accumulation was determined on the incisors of half the animals during only the last 3 days of the study and on the remaining animals at the conclusion of a 21-day test period when both sulcal and smooth-surface caries were assessed. No significant differences between the test groups in food consumption were observed nor were there any differences in body weight gain. The least amount of plaque was observed in the animals given monolaurin; the other fatty acids exerted no significant effect upon plaque accumulation. The smooth-surface caries data indicated that the least number of lesions occurred in the animals on the diet containing monolaurin. Nonanoic acid was significantly more effective in limiting sulcal caries than any of the other fatty acids studied. Thus both monolaurin and nonanoic acid have significant cariostatic activity in the rat.     

1-Tetradecanol complex reduces progression of Porphyromonas gingivalis-induced experimental periodontitis in rabbits

BACKGROUND: It has been recently shown that monounsaturated fatty acids inhibit endothelial activation and reduce tissue responsiveness to cytokines. The present study has been planned to investigate topical application of a novel monounsaturated fatty acid complex (1-tetradecanol complex) for prevention of Porphyromonas gingivalis-induced periodontitis in rabbits. METHODS: Experimental periodontitis was induced in New Zealand white rabbits with silk sutures tied around the mandibular second premolars bilaterally, followed by the topical application of 10(9) colony forming units (CFU) of P. gingivalis. 1-Tetradecanol complex (1-TDC) was topically applied at 1- and 10-mg/ml concentrations in five animals in each group, whereas control animals received olive oil vehicle (five animals) three times per week for 6 weeks. Negative controls included ligature alone (14 animals) or ligature + P. gingivalis (non-treatment; 15 animals). Rabbits were sacrificed after 6 weeks, and mandibular block sections were obtained; tissues were decalcified and embedded in paraffin. Thin sections (5 microm) were stained with hematoxylin and eosin or tartrate-resistant acid phosphatase. Macroscopic and histologic evaluation of samples was followed by the characterization of cellular inflammatory infiltrate and quantitative histomorphometric measurements. RESULTS: Treatment with both concentrations of 1-TDC and vehicle resulted in significant prevention of macroscopic periodontal inflammation and bone loss (75%; P <0.05) compared to the non-treatment (ligature + P. gingivalis) group, where significant periodontal tissue destruction characterized by attachment and bone loss was detected. However, there was no statistically significant difference between the vehicle and both 1-TDC groups. Histologically, 1-TDC inhibited inflammatory cell infiltration and prevented osteoclastogenesis, whereas treatment with vehicle did not show the same effect as in the 1-TDC groups; the difference between vehicle and the higher concentration of 1-TDC (10 mg/ml) was statistically significant. CONCLUSION: Topical application of an esterified monounsaturated fatty acid complex (1-TDC) was found promising in preventing bone loss, inflammatory cell infiltration, and connective tissue destruction in the rabbit periodontitis model.     

Odontoblast metabolism in rats deficient in vitamin D and calcium. IV. Lysosomal and energy metabolic enzymes

Young rats, fed a low calcium and vitamin D deficient diet for 2 weeks, developed hypocalcemia, an increased activity of serum alkaline phosphatase and an increase in the serum concentration of immunoreactive parathyroid hormone. An increased activity of lactate dehydrogenase and cytochrome oxidase in odontoblasts was found. No shift in the general energy metabolic pathway was found as visualized in the lactate dehydrogenase iso-enzyme pattern. The dominating lactate dehydrogenase isoenzyme in odontoblasts from both the normal and the deficient rats was LDH 1 (H4, LD5), thus indicating primarily an aerobic energy-metabolism Also the activities of the lysosomal enzymes acid phosphatase, cathepsin D and hyaluronidase in the odontoblasts from the deficient animals were increased when compared to the normal animals. No significant change could be demonstrated for beta-glucuronidase and beta-N-acetylglucosaminidase. It was earlier found that this deficient diet caused an increase in odontoblast alkaline phosphatase activities and protein synthesis in vitro. In view of the present findings it might be concluded that the low calcium and vitamin D deficient diet causes a general increase in the odontoblast metabolism. It is not known whether this is due to the increase in parathyroid hormone or if it is a direct effect of the lowered serum calcium concentration.     

Frontal bone advancement and compensatory craniofacial growth changes in rabbits with experimental coronal suture immobilization.

Recent clinical advances in the surgical correction of coronal suture synostosis involve the overcorrection of a frontal bone segment to allow for unrestricted expansion of the developing neurocapsular matrix. However, the effects of such large-scale calvarial repositioning on subsequent brain mass growth trajectories and compensatory cranio-facial growth changes is unclear. This study was designed to investigate this relationship in an experimental rabbit model of bilateral coronal suture synostosis. Amalgam markers were placed across the frontonasal, coronal, and anterior lambdoid sutures in thirty-one 1.5-week-old rabbits. Twenty-one animals underwent bilateral coronal suture immobilization using methyl-methacrylate. Ten animals were left untreated and served as sham controls. At 6 weeks of age, the coronal suture was released by frontal bone craniotomy or frontal bone craniotomy with a 6-mm frontal bone advancement. Lateral head radiographs were taken at 1.5, 6, 7, 9, 12, and 18 weeks of age. Results revealed that by 6 weeks of age, animals with coronal suture immobilization exhibited growth disturbances across the various sutures resulting in altered craniofacial and cranial vault shape compared to control animals. Following coronal suture release, animals that underwent craniotomy showed rapid restenosis, which resulted in significantly altered cranial vault shape and cranial orthocephalization by 18 weeks of age. Animals that underwent frontal bone advancement exhibited normal overall craniofacial growth by 18 weeks of age compared with control animals but did exhibit regional compensatory growth disturbances at the frontonasal and anterior lambdoid sutures, possibly related to neural tissue distension.(ABSTRACT TRUNCATED AT 250 WORDS)     

Wound healing and wound contraction after palatal surgery and implantation of poly-(L-lactic) acid membranes in beagle dogs.

The effect of implantation of poly-(L-lactic) acid membranes on wound healing and wound contraction after palatal surgery was investigated macroscopically in beagle dogs. Thirty beagle dogs were randomly assigned to two experimental groups (group L and LM; both n = 12) and a control group (group C; n = 6). At 12 weeks of age, a soft-tissue defect was created in the median region of the palate by excising a standardized elliptical mucoperiosteal flap. This defect was closed according to the Von Langenbeck technique, leaving two areas of denuded bone. Immediately after surgery, poly-(L-lactic) acid membranes were implanted on the denuded bony areas in the animals of the LM group. In the L group, no poly-(L-lactic) acid membrane was used. Tattoo points were placed in the mucoperiosteum on opposite wound margins in all groups to quantify wound contraction. Standardized intraoral photographs were taken at regular intervals. Wound surface areas and weekly increments of the distance between the tattoo points were calculated. Clinical wound healing was significantly retarded in animals of the LM group. Wound contraction was comparable in both experimental groups and was restricted to the first 2 weeks after surgery. Corresponding lateral migration of the tattoo points in the median region of the palate in these groups occurred in the first week after surgery, followed by wound contraction in the second week. Implantation of poly-(L-lactic) acid membranes following palatal wounding in beagle dogs had no beneficial short-term effects on wound healing and contraction.     

A biochemical analysis of parotid and submandibular salivary gland function with age after simultaneous stimulation with pilocarpine and isoproterenol in female NIA Fischer 344 rats.

This analysis of physiological, biochemical and molecular changes related to aging was made in 3-, 12- and 24-month-old rats. The salivary gland weight/body weight ratio and the structural membrane proteins did not change with age for either gland, but a significant age-related decline in DNA synthesis for both glands was detected, unrelated to the hormonal responsiveness at the level of the plasma membrane. There was a marked increase in the concentration of soluble proteins in adolescent parotid gland and, for the two older age groups, in submandibular gland. The saliva flow rate was different when expressed as volume per time, as volume per time and g glandular wet weight, and/or kg body weight. The concentration of secreted proteins was not affected by age in either gland. The total amount of proteins secreted over 30 min revealed no age-related perturbation for the parotid gland, but showed a significant age-related increase in submandibular saliva. Sodium dodecyl sulphate-polyacrylamide gel analysis revealed changes in the protein bands between 39 and 50 kDa in the Coomassie blue-stained gels from 12-month-old animals. Amylase showed an initial increase (12 months), followed by a marked decline in its activity in parotid saliva. The glandular supernatant had low residual cellular amylase activity after stimulation. Therefore, secretory impairment with age after pilocarpine-isoproterenol stimulation was excluded. Analysis of total RNA showed a pronounced decrease of amylase mRNA in the parotid gland between 12 and 24 months of age. No amylase mRNA was expressed in any of the submandibular samples. For epidermal growth factor, total saliva showed a decrease with age. It seemed that the submandibular gland followed the same picture with age as the parotid gland, with a specific decline in the biosynthesis of single secretory proteins.     

Relationship between smoking and folic acid, vitamin B12 and some haematological variables in patients with chronic periodontal disease

AIM: The purpose of this study was to investigate the relationship between cigarette smoking and the serum levels of folic acid, vitamin B(12) and some haematological variables in patients with periodontal disease. PATIENTS AND METHODS: The study base consisted of 88 volunteer patients with periodontal disease, including 45 current smokers in the age range 31-68 years and 43 non-smokers in the range 32-66 years. The clinical parameters included plaque index (PI), gingival index (GI), bleeding on probing (BOP), probing depth (PD) and clinical attachment loss (CAL). Folic acid, vitamin B(12) and haematological variables were determined from peripheral blood samples. RESULTS: PI, PD and CAL means were significantly higher in smokers than non-smokers (p<0.05). The serum folic acid concentration of smokers was lower than that of non-smokers (p<0.05), whereas the white blood cell count was higher in smokers than in non-smokers (p<0.05). CONCLUSION: The results of this study suggest that among patients with periodontal disease the serum folic acid concentration is lower in smokers compared with non-smokers.     

Effect of desalivation and age on susceptibility to infection by Streptococcus sobrinus

The influence of desalivation and age on susceptibility to infection by Streptococcus sobrinus was studied using 80 Sprague-Dawley female rats weaned at age 21 days. Forty animals (donors) were infected with S. sobrinus 6715 (ATCC 27352), formed into ten groups of 4, fed diet 2000, and offered 10% sucrose water ad libitum. The remaining 40 animals were fed laboratory chow and sterile distilled water until introduced into the experiment. When the animals were aged 25 days, 10 noninfected animals were anesthetized, desalivated, and caged with 10 infected (donor) animals (group I). On day 36 these procedures were repeated on the remaining animals (group II). Infection was checked daily. Animals were regarded as infected when S. sobrinus was detected on 2 consecutive days and confirmed 1 week later. Animals were killed, jaws dissected, and populations of S. sobrinus and total bacterial viable count of each jaw estimated. The average number of days from pairing to detecting infection (2 consecutive days) was as follows: group I (age 25 days): desalivated 5.4 (SD 2.5), intact 8.8 (SD 4.5); group II (age 36 days): desalivated 7.8 (SD 2.9). Only 3 intact animals became infected in group II after a total elapsed time of 21 days. The mean viable counts of S. sobrinus per jaw in group 1 were as follows: desalivated 3.6 x 10(6) (SD 4.1); donor cagemate 13.0 x 10(6) (SD 9.7); intact 0.26 x 10(6) (SD 0.39); donor cagemate 4.5 x 10(6) (SD 4.3). Desalivated animals tended to be more heavily infected than intact animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

A histological study of the effect of growth hormone on odontogenesis in the Lewis dwarf rat

The effect of growth hormone (GH) on the dentition has been described in children with pituitary dwarfism where teeth fail to form; those that do form tend to be reduced in size and the eruption potential is diminished. The aim here was to examine the effect of GH on odontogenesis via molar development in Lewis (control), dwarf (Dw) and Dw GH-treated (Dw+GH) rats aged 3, 6, 9, 12 and 15 days. Dw+GH animals received a twice-daily dose (65 microg/kg) of GH which commenced at 2 days of age. Animals were killed, mandibles removed, processed to embedding in paraffin, sectioned and stained for histological examination of molar morphology during development. Variations in enamel mineralization and root development were observed. In 6-day-old animals, enamel mineralization was delayed in Dw and Dw+GH animals. Root initiation was evident at 6 days of age in controls but was not observed until 9 days of age in Dw and Dw+GH animals. At 12 days of age, maturation of enamel in Dw and Dw+GH animals remained delayed. By 15 days of age no variation in tooth development was evident. These data indicate that enamel mineralization is affected by the level of circulating GH in the rat. A specific deficiency of GH did not appear to delay bone resorption prior to tooth emergence.     

Reduced growth hormone receptor immunoreactivity in osteoclasts adjacent to the erupting molar in the incisor-absent (osteopetrotic) rat

First molars fail to erupt in the incisor-absent (ia/ia) rat because of a defect in osteoclast function. Growth factors that regulate local bone metabolism include growth hormone (GH), insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and interleukin-1 alpha (IL-1alpha). Since osteoclast function may be affected by these factors, the aim of this study was to determine the distribution of GH receptor (GHr), IGF-I, EGF and IL-1alpha, in osteoclasts located occlusal to the erupting first molar, in the 'eruption pathway', in normal and ia/ia rats. Sagittal sections of the first molar and adjacent bone from 3- and 9-d-old animals were examined. Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP). The TRAP-positive osteoclast cell numbers were higher in ia/ia animals at 3 and 9 days-of-age. In the ia/ia group, fewer osteoclasts were GHr- and IGF-I-positive at 3 d of age, and at 9 d of age fewer osteoclasts were GHr-positive. In the ia/ia rat, defective osteoclast function failed to resorb bone to provide an eruption pathway for the lower first molar. The expression of GHr, and to some degree IGF-I, by these osteoclasts was reduced, which may be related to their ability to differentiate and function.     

Odontoblast metabolism in rats deficient in vitamin D and calcium. IV. Lysosomal and energy metabolic enzymes

Abstract Young rats, fed a low calcium and vitamin D deficient diet for 2 weeks, developed hypocalcemia, an increased activity of scrum alkaline phosphatase and an increase in the serum concentration of immunoreactive parathyroid hormone. An increased activity of lactate dehydrogenase and cytochrome oxidase in odontoblasts was found. No shift in the general energy metabolic pathway was found as visualized in the lactate dehydrogenase iso-enzyme pattern. The dominating lactate dehydrogenase iso-enzyme in odontoblasts from both the normal and the deficient rats was LDH I (H₄, LD₅), thus indicating primarily an aerobic energy-metabolism. Also the activities of the lysosomal enzymes acid phosphatase, cathepsin D and hyaluronidase in the odontoblasts from the deficient animals were increased when compared to the normal animals. No significant change could be demonstrated for β-glucuronidase and β-N-acetylglucosaminidase. It was earlier found that this deficient diet caused an increase in odontoblast alkaline phosphatase activities and protein synthesis in vitro. In view of the present findings it might be concluded that the low calcium and vitamin D deficient diet causes a general increase in the odontoblast metabolism. It is not known whether this is due to the increase in parathyroid hormone or if it is a direct effect of the lowered serum calcium concentration.