An adaptation of the Lashley cup for use in rat saliva collection

Contrasting Dose-rate Effects of γ-irradiation on Rat Salivary Gland Function

The aim of this study was to investigate the effects of 60Co irradiation delivered at high (HDR) and low (LDR) dose-rates on rat salivary gland function. Total-body irradiation (TBI; total doses 7.5, 10 and 12.5 Gy) was applied from a 60Co source at dose-rates of 1 cGy/min (LDR) and 40 cGy/min (HDR) followed by syngeneic bone marrow rescue. Four days before and 1-30 days after TBI, submandibular and parotid saliva samples were collected in male albino Wistar rats using Lashley cups. Lag phase and flow rate were recorded, and [Na+] and [K+] were measured. The severity of salivary gland dysfunction for each dose-rate was dependent on total TBI dose in all parameters. LDR irradiation significantly enhanced the increase of lag phase, while it tended to further decrease flow rate during days 0-3. At later times the reverse effect was seen with significant LDR sparing in most cases. The changes in [Na+] and [K+] showed similar trends; LDR had an enhancing effect for early damage, while beyond day 3 it consistently produced less damage. From this dose-rate study it is concluded that the early postirradiation changes in salivary gland function are probably predominantly caused by irradiation damage to membrane structures and are less the result of reproductive failure. The later changes in salivary gland function are probably mainly dependent on repopulation of surviving stem cells.

Optimum dose range for the amelioration of long term radiation-induced hyposalivation using prophylactic pilocarpine treatment

BACKGROUND

To determine dose and time dependency of pilocarpine pre-treatment protection from late damage after unilateral irradiation of the rat parotid gland.

METHODS AND MATERIALS

The right parotid gland of saline (1mg/ml) or pilocarpine (4 mg/kg) pre-treated rats was irradiated with 10, 15 and 20 Gy. Saliva was collected from the irradiated and shielded parotid before, 30, 60, 120 and 240 days after irradiation. The number of acinar cells/gland was determined 30, 120 and 240 days after irradiation by histological examination.

RESULTS

Pilocarpine pre-treated rats, protection of parotid gland function was seen in the early-intermediate phase (0-120 days) after 15 Gy and in the late phase (>120 days) after 10 and 15 Gy. Although no protection was observed after 20 Gy, a stimulatory effect of pilocarpine on the non-irradiated gland resulted in a significant increase in total saliva secretion. The increase in function after pilocarpine treatment was paralleled by a significant increase in the number of acinar cells in both the irradiated and shielded glands.

CONCLUSIONS

Pre-irradiation treatment with pilocarpine induces compensatory response, at lower doses, in the irradiated and at higher doses in the non-irradiated gland reducing late damage, due to stimulation of unirradiated or surviving cells to divide.

Analysis of the human saliva proteome

Interest in the characterization of the salivary proteome has increased in the last few years. This review discusses the different techniques and methodologies applied to the separation and identification of salivary proteins. Nowadays, proteomic techniques are the state of the art for the analysis of biologic materials and saliva is no exception. 2D electrophoresis and tryptic digest analysis by mass spectrometry are the typical methodology, but new approaches using 2D liquid chromatography/mass spectrometry methods have already been introduced for saliva analysis. Due to their important physiologic role in the oral cavity, low-molecular-weight proteins and peptides are also included in this article and the methodologies discussed.

Radioprotective effect of amifostine on parotid gland functioning is region dependent

PURPOSE

To investigation the protective ability of amifostine during partial irradiation of the rat parotid gland.

METHODS AND MATERIALS

Single-dose X-ray irradiation was performed by use of collimators with conformal radiation portals for either the 100% volume (15 Gy) or the 50% cranial/caudal partial parotid gland volumes (30 Gy). Amifostine was administered intraperitoneally at a dose of 250 mg per kg body weight, 25 minutes before irradiation. Saliva flow rates, gland weights, and the tissues of the individual lobes were investigated up to 1 year after treatment.

RESULTS

A clear protective effect of amifostine was found against loss of saliva flow, the altered appearance of gross morphology, loss of gland weight, and histopathologic changes for the 100% volume gland irradiations and for the 50% volume cranial irradiations but not for the 50% volume caudal irradiations.

CONCLUSIONS

The protective ability of amifostine is strongly dependent on the irradiated glandular region and observed for later damage only. The major effect of the drug seems to be the prevention of volume effects caused by secondary damage that occurs in shielded parts of the gland. The results of the present study show that understanding of the anatomy and physiology of organs that are to be spared is necessary to ensure optimal preservation of function.

Secondary radiation damage as the main cause for unexpected volume effects: a histopathologic study of the parotid gland

PURPOSE

To elucidate with a histopathological study the mechanism of region-dependent volume effects in the partly irradiated parotid gland of the rat.

METHODS AND MATERIALS

Wistar rats were locally X-irradiated with collimators with conformal radiation portals for 100% volume and 50% cranial/caudal partial volumes. Single doses up to 40 Gy were applied. Parotid saliva samples were collected, and the three lobes of the parotid gland were examined individually on the macro- and micromorphologic level up to 1 year after irradiation.

RESULTS

Dose-dependent loss of gland weight was observed 1 year after total or partial X-irradiation. Weight loss of the glands correlated very well with loss of secretory function. Irradiating the cranial 50% volume (implicating a shielded lateral lobe) resulted in substantially more damage in terms of weight loss and loss of secretory function than 50% caudal irradiation (shielding the ventral and dorsal lobe). Histologic examinations of the glands 1 year after irradiation revealed that the shielded lateral lobe was severely affected, in contrast to the shielded ventral and dorsal lobes. Time studies showed that irradiation of the cranial 50% volume caused late development of secondary damage in the shielded lateral lobe, becoming manifest between 240 and 360 days after irradiation. The possible clinical significance of this finding is discussed.

CONCLUSION

It is concluded that the observed region-dependent volume effect for late function loss in the rat parotid gland after partial irradiation is mainly caused by secondary events in the shielded lateral lobe. The most probable first step (primary radiation event) in the development of this secondary damage is radiation exposure to the hilus region (located between the ventral and dorsal lobe). By injuring major excretory ducts and supply routes for blood and nerves in this area, the facility system necessary for proper functioning of the nonexposed lateral lobe is seriously affected. The unexpected volume effect in the rat might have consequences for treatment strategies in radiotherapy, implicating not only salivary glands but also other organs with a seemingly homogeneous distribution of radiosensitive elements, a situation wherein volume effects have not been anticipated up to now.

Volume effects and region-dependent radiosensitivity of the parotid gland

PURPOSE

To detect volume effects and possible regional differences in radiosensitivity of the rat parotid gland.

METHODS AND MATERIALS

Parotid glands of male albino Wistar rats were locally X-irradiated, with collimators with conformal radiation portals used to supply 100% volume and 50% cranial/caudal partial volumes. High-resolution magnetic resonance imaging was used to provide the outlines of the parotid glands. Single doses of up to 40 Gy were applied, and the effects on saliva secretion, measured with the aid of miniaturized Lashley cups, were followed up to 365 days after the irradiation.

RESULTS

Under conditions of equal mean absorbed doses and small variations in dose distribution, a pertinent volume effect was observed for late but not for early radiation damage. The late effects were different for the cranial part as compared with the caudal part of the parotid gland. The reduction in flow rate was much more severe after irradiation in the cranial part. After a single dose of 30 Gy, the reductions in flow rates were approximately 65% and 25% for the cranial and caudal parts, respectively. At that dose, no saliva flow was observed after irradiation of 100% of the gland.

CONCLUSION

From the rat model studies presented, it is concluded that late radiation damage after partial irradiation of parotid glands shows region-dependent volume effects. This finding is expected to be relevant to the radiosensitivity of human salivary glands, and it implies that the predictive power of the mean dose concept in radiotherapeutic practice is limited. The finding of region-dependent late radiation damage also challenges the basic assumptions of most current normal tissue complication probability models for parotid gland function.

Opposite effects of antidepressants on unstimulated and stimulated salivary flow

In this study, effects on both stimulated and non-stimulated salivary flow as well as salivary components of different antidepressant drugs were compared. Rats received imipramine (IMI; 10mg/ml), fluoxetine (FLU; 20 mg/ml) or moclobemide (MOC; 30 mg/ml) by gavage. The drugs were administered 24, 5 and 1 h before saliva collection (sub-acute treatment) or as a once a day treatment for 14 days (chronic treatment). Animals were sedated with thiopental and saliva was collected using pre-weighed cotton balls inserted in the mouth for 1 min before and after pilocarpine stimulus. Pilocarpine-stimulated saliva was also collected for biochemical assays of total proteins, amylase, phosphate and calcium, performed through automated colorimetric methods. Non-stimulated salivary flow was decreased by sub-acute IMI 10 mg/kg treatment. Pilocarpine-stimulated salivary flow was significantly increased by acute treatments with IMI, FLU and MOC in comparison to the control group. The same opposite pattern of effects on non-stimulated and pilocarpine-stimulated salivation was seen after chronic treatment with the antidepressants. Increased levels of calcium following sub-acute treatment with IMI and after prolonged treatment with FLU and MOC were detected. In the assayed samples, phosphate was found to be increased following chronic treatment with FLU or MOC. These results may explain the discrepant effects of the antidepressants on salivation described in pre-clinical and clinical studies.

Comparison of radiosensitivity of rat parotid and submandibular glands after different radiation schedules

BACKGROUND AND PURPOSE

To investigate the radiosensitivity of rat parotid and submandibular gland functioning after local single dose, conventional fractionated and accelerated fractionated irradiation.

METHODS

The salivary glands of male albino Wistar rats were locally irradiated with a single dose (15 Gy) or a calculated (alpha/beta; 9.6) biological effective dose of fractionated irradiation equal to this, viz. conventional fractionation (32 Gy in 16 fractions of 2 Gy/day, five times/week) or accelerated fractionation (32 Gy in 16 fractions of 2 Gy, two fractions/day). Parotid and submandibular/sublingual saliva samples were collected by means of miniaturized Lashley cups before and up to 240 days after irradiation. Salivary flow rate, lag phase and amylase secretion were used as parameters for the assessment of salivary gland function. At the end of the experiments the animals were sacrificed and the glands processed for histopathological examination.

RESULTS

Up to 120 days after irradiation no differences were observed between the glands or between the different irradiation schedules. Beyond 120 days, however, the parotid gland performed better in flow rate and lag phase after fractionated irradiation, when compared to the submandibular gland. The observed differences in function corresponded with the observed late histopathological changes. The parotid gland contained more acinar cells and had a higher gland weight. No differences were observed between both fractionation schedules on each gland.

CONCLUSIONS

The main observation from this study is the higher radiosensitivity of the submandibular gland compared to the parotid gland for late effects after fractionated irradiation. This may have implications for the treatment planning in case of radiotherapy for head and neck cancer.

Measuring short-term gamma-irradiation effects on mouse salivary gland function using a new saliva collection device

A restraining device was designed specifically for the collection of whole saliva from mice without using anesthesia. As the procedure does not involve surgical cannulation of the salivary glands, saliva can be collected from the same mouse at different times. The time between the injection of a secretory stimulant (pilocarpine) and the appearance of saliva in the mouth (lag time) was 100.5 +/-8.5 s (mean+/-S.E.M., n=10) for control mice. The volume of saliva collected in the first 5 min was three times greater than that collected between 15 and 20 min. The average flow rate for a collection period of 15 min was 16.7 +/-1.8 microl/min (n=10). The flow rate was decreased 50% (P<0.005) whereas the lag time was increased more than 300% (P<0.05) at 24 h after irradiation. The concentrations of a 23.5-kDa protein and a mucin were decreased after irradiation whereas there was no significant effect on the concentration of amylase or peroxidase.

Early to late sparing of radiation damage to the parotid gland by adrenergic and muscarinic receptor agonists

Damage to salivary glands after radiotherapeutic treatment of head and neck tumours can severely impair the quality of life of the patients. In the current study we have investigated the early-to-late pathogenesis of the parotid gland after radiation. Also the ability to ameliorate the damage using pretreatment with adrenergic or muscarinic receptor agonists is studied. Rats were locally irradiated with or without i.p. pretreatment with phenylephrine (alpha-adrenoceptor agonist, 5 mg kg(-1)), isoproterenol (beta-adrenoceptor agonist, 5 mg kg(-1)), pilocarpine (4 mg kg(-1)), methacholine (3.75 mg kg(-1)) (muscarinic receptor agonists) or methacholine plus phenylephrine. Parotid salivary flow rate, amylase secretion, the number of cells and gland histology were monitored sequentially up to 240 days postirradiation. The effects were described in 4 distinct phases. The first phase (0-10 days) was characterised by a rapid decline in flow rate without changes in amylase secretion or acinar cell number. The second phase (10-60 days) consists of a decrease in amylase secretion and is paralleled by acinar cell loss. Flow rate, amylase secretion and acinar cell numbers do not change in the third phase (60-120 days). The fourth phase (120-240 days) is determined by a further deterioration of gland function but an increase in acinar cell number, albeit with poor tissue morphology. All drug pretreatments used could reduce radiation effects in phase I and II. The protective effects were lost during phase IV, with the exception of methacholine plus phenylephrine pretreatment. The latter combination of drugs ameliorated radiation-damage throughout the entire follow-up time. The data show that combined pre-irradiation stimulation of muscarinic acetylcholine receptors with methacholine plus alpha-adrenoceptors with phenylephrine can reduce both early and late damage, possibly involving the PLC/PIP2 second messenger pathways. This opens perspectives for the development of clinical applicable methods for long-term sparing of parotid glands subjected to radiotherapy of head and neck cancer patients.

Early radiation effects on muscarinic receptor-induced secretory responsiveness of the parotid gland in the freely moving rat

Although the salivary glands have a low rate of cell turnover, they are relatively radiosensitive. To study the possible mechanism behind this inherent radiosensitivity, a rat model was developed in which saliva can be collected after local irradiation of the parotid gland without the use of anesthetics or stressful handling. Saliva secretion was induced by the partial muscarinic receptor agonist pilocarpine (0.03-3 mg/kg) with or without pretreatment with the beta-adrenoceptor antagonist propranolol (2.5 mg/kg), or the full muscarinic receptor agonist methacholine (0.16-16 mg/min), and measured during 5 min per drug dose before and 1, 3, 6 and 10 days after irradiation. The maximal secretory response induced by pilocarpine plus propranolol was increased compared to that with pilocarpine alone but did not reach the level of methacholine-induced secretion, which was about five times higher. One day after irradiation a decrease in maximal pilocarpine-induced secretion was observed (-22%) using the same dose of pilocarpine that induces 50% of the maximal response (ED(50)), in both the absence and presence of propranolol, indicating that the receptor-drug interaction was not affected by the radiation at this time. The secretory response to methacholine 1 day after irradiation, however, was normal. At day 3 after irradiation, the maximal methacholine-induced secretion was also affected, whereas pilocarpine (+/-propranolol)-induced maximal secretion decreased further. At day 6 after irradiation, maximal secretory responses had declined to approximately 50% regardless of the agonist used, whereas ED(50) values were still unaffected. No net acinar cell loss was observed within the first 10 days after irradiation, and this therefore could not account for the loss in function. The results indicate that radiation does not affect cell number or receptor-drug interaction, but rather signal transduction, which eventually leads to the impaired response. We hypothesize that the early radiation effect, within 3 days, may be membrane damage affecting the receptor-G-protein signaltransfer. Later critical damage, however, is probably of a different nature and may be located in the second-messenger signal transduction pathway downstream from the G protein, not necessarily involving cellular membranes.

Preservation of the rat parotid gland function after radiation by prophylactic pilocarpine treatment: radiation dose dependency and compensatory mechanisms

PURPOSE

To study the ability of a prophylactic pilocarpine administration to preserve the rat parotid gland function after unilateral irradiation with graded doses of X-rays.

METHODS

The right parotid gland of male albino Wistar rats was irradiated with single doses of X-rays (10-30 Gy, at 1.5 Gy min(-1)). Pilocarpine (4 mg/kg) was administered intraperitoneally, 1 hour prior to irradiation. Saliva samples of both left and right parotid gland were collected by means of miniaturized Lashley cups 4 days before and 3, 7, 10, and 30 days after irradiation. The parotid salivary flow rate (microl/min) was used as a parameter for the assessment of parotid gland function.

RESULTS

Our data confirm that a single prophylactic treatment of pilocarpine can attenuate radiation-induced loss of gland function. Surprisingly, the effect of pilocarpine was not restricted to the irradiated gland only. Pilocarpine also enhanced the flow rate in the contralateral, nonirradiated gland. The latter effect was found for all doses above 10 Gy and became apparent around 7 days after the radiation treatment. The effectiveness of pilocarpine to attenuate function loss in the irradiated gland decreased with increasing dose and was lost after single doses of 30 Gy.

CONCLUSIONS

Our data provide direct evidence that increasing the compensatory potential of the nondamaged gland, at least in part, underlies the "radioprotective effect" of pilocarpine in case of unilateral radiation. The ability of pilocarpine to ameliorate the early radiation-induced impairment of the parotid gland function in the irradiated gland may therefore be dependent on the remaining number of functional cells, and thus on the volume of the gland that lies within the radiation portal.

Quantification of transforming growth factor-beta in biological material using cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct

Transforming growth factor-beta (TGF-beta), a multifunctional cytokine, can be quantified by a variety of bioassays or immunoassays. One of the disadvantages of these techniques is that they require sample purification to remove components that interfere with the TGF-beta signal. In the current study the feasibility of quantifying TGF-beta in complex biological fluids directly with a recently developed bioassay was examined. This assay is based on the ability of TGF-beta to induce plasminogen activator inhibitor-1 (PAI-1) expression. Mature TGF-beta binds to the receptors of mink lung epithelial cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct (PAI/L), resulting in a dose-dependent increase of luciferase activity. Specificity for TGF-beta was proven by treatment of the samples with neutralizing antibodies. The sensitivity and the intraassay precision are comparable to the ELISA. It is demonstrated, however, that, unlike the ELISA, a purification step by, e.g., acid-ethanol extraction prior to the PAI/L assay, is not required. This not only simplifies the assay but also reduces the minimal sample volume and allows to discriminate between latent and mature TGF-beta. The present study furthermore provides insight in the critical steps for accurate TGF-beta determination, which include careful blood collection and sample handling (storage and preparation). With this protocol TGF-beta has been quantified in human plasma, rat plasma, rat saliva, tissue extracts from rat lung, and in culture medium of TGF-beta-producing cells.

Acute irradiation effects on morphology and function of rat submandibular glands

In this study the morphologic and functional changes were compared after irradiation (single dose, 15 Gy) of rat submandibular salivary glands. Before and 1-10 days after local irradiation of the gland region, samples of submandibular saliva were collected after stimulation by pilocarpine. At the same time-points and also 3 h postirradiation submandibular glands were carefully extirpated and prepared for histocytologic examination (LM, TEM). Maximal increase of the lag phase and decrease of the flow rate were observed 3 days after irradiation, while [K+] and [Na+] increased and decreased, respectively, from days 1 and 3 after irradiation. Morphologic changes were observed from the third hour after irradiation, were maximal 3 days after irradiation and had partially recovered by day 10. Three hours and 1 day after irradiation degranulation of convoluted granulated tubes (CGT) was observed. Three days after irradiation the most striking morphologic changes in serous and mucous cells were distension of the cisternae of the RER, degeneration of mitochondria and vacuolization of the cytoplasm. Fibril-like condensations of electron dense material in the mucous granules were observed 3 h, 1 and 6 days after irradiation. Regranulation of CGT cells was observed from day 6. From this study it is concluded that changes in salivary gland function can be observed before major morphologic changes occur. Functional changes persist after the morphologic changes seem to have virtually returned to normal.