The influence of PTH, calcium gluconate and EDTA on the parotid saliva in the goat

1. The role of exogenous parathyroid hormone (PTH) and stimulation or inhibition of endogenous hormone release, on the parotid gland of normal and thyroparathyroidectomized (t.x.p.t.x.) goats was studied. 2. The intravenous infusion of PTH and EDTA produced a transitory rise in saliva flow rate in intact animals. In t.x.p.t.x. goats the flow of saliva decreased transiently throughout the infusion. 3. The calcium levels in parotid saliva was unchanged throughout the infusion of PTH, EDTA, calcium gluconate both alone or with propranolol, in either intact or t.x.p.t.x. animals. 4. The parathyroid hormone infusion caused an increase in salivary phosphate concentration in both intact and operated goats. The effects of PTH upon the salivary flow and concentration of P are discussed.     

The composition and flow of parotid saliva during acute hyperkalaemia in sodium-deficient sheep.

Sheep were infused intravenously with 0-43 M-KCl at 2 ml/min for 2 hr while they were either sodium-replete or sodium-deficient after the unilateral loss of parotid saliva for 18 hr or 3 days. Salivary flow was depressed during potassium infusion and the flow rates observed at maximum hyperkalaemia were similar in all three states of sodium balance despite the large differences in flow rate before potassium infusion. The fall in salivary Na/K ratio during potassium administration was diphasic, the initial decline being slow and followed by a more rapid fall in the ratio. The duration of the initial period of slow decline in this ratio ranged from 75-105 min, 45-60 min, and about 15 min in the sodium-replete, mildly sodium-deficient and severely sodium-deficient states respectively. The decline in salivary flow during sodium depletion was associated with decreasing salivary bicarbonate concentration and increasing salivary phosphate and hydrogen ion concentrations with the concentration of chloride showing no consistent trend. During acute hyperkalaemia the chloride and phosphate concentrations were negatively correlated with salivary flow, the bicarbonate concentration was positively correlated with flow and the hydrogen ion concentration was unaltered. The sodium concentration of the saliva showed a statistically significant correlation with flow only when the sheep were severely sodium-deficient.     

A comparison of the effects of vasoactive intestinal polypeptide on secretion from the submaxillary gland of the sheep and pig

The effects, on secretion of fluid and protein from the submaxillary gland of intracarotid injections of acetylcholine or vasoactive intestinal polypeptide (VIP), and intracarotid infusions of VIP during a background of muscarinic stimulation, were examined in sheep and pigs. Intracarotid injections of VIP produced secretion of saliva from the ovine gland which continued after administration of atropine, phentolamine and propranolol. The protein concentration of this saliva was over 5-fold greater than that secreted in response to acetylcholine. Intracarotid injection of VIP did not evoke secretion from the porcine submaxillary gland but increased 3-fold the protein concentration in saliva evoked by subsequent intracarotid injection of acetylcholine. Intracarotid infusions of VIP in sheep produced dose-related increases in both flow (up to 1.9-fold) and protein concentration (up to 42-fold) of submaxillary saliva secreted in response to a background infusion of bethanechol. In pigs, intracarotid infusions of VIP at 0.015, 0.15 and 1.5 nmol/min produced increases in both flow and protein concentration of bethanechol-evoked saliva. The increases in protein concentration (up to 2.8-fold) were dose-related, but the increases in flow were not, being ca. 25% with each dose of VIP. The experiments provide evidence that VIP may effect mobilization of protein into saliva even in a species (pig) in which VIP does not evoke secretion of fluid.     

Analysis of parotid and mixed saliva in Roe deer (Capreolus capreolus L.)

In ruminants, different functions have been ascribed to the different salivary glands according to the feeding type. In this context, possible adaptations of salivary functions were investigated regarding the secretion of various proteins by different types of salivary glands. To yield uncontaminated parotid saliva in large quantities, a non-surgical method has been developed. Parotid gland secretions were collected via endoscopic placement of guide wires into each parotid duct, which were subsequently used for placement of collection catheters. Salivary flow was stimulated by intra-glandular administration of the parasympathomimetic compound pilocarpine-hydrochloride into the parotid gland. Mixed saliva (excluding parotid saliva) was collected into sterile tubes by normal outflow during the sampling of parotid saliva. The total flow volume, flow rate and the content of proteins as well as of several ions (Na⁺, K⁺, Ca²⁺, inorganic phosphate) of both types of saliva were measured in sheep, fallow deer and roe deer. Roe deer secreted the highest amount of total salivary proteins relative to body mass [mg/kg body mass] and the highest relative volume [ml/10 min/kg body mass], both in parotid and mixed saliva, of all ruminant species examined. Additionally, the protein profile and the tannin-binding properties of parotid and mixed saliva in roe deer were investigated. Parotid saliva bound almost twice as much tannin as mixed saliva, underlining the importance of yielding uncontaminated parotid saliva for tannin-binding studies. Accepted: 6 January 1998     

The role of the autonomic nervous system in the depression of parotid salivary secretion during hyperkalaemia in conscious sheep.

The rate of flow and electrolyte concentration of parotid saliva were measured before, during and after intravenous and contralateral intracarotid infusion of KCl (0.5 mol.1(-1)) and NaCl (0.5 mol.1(-1)) at 385-625 mumol. min(-1) for 40 min into 5 sheep. In intact conscious sheep contralateral intracarotid infusion of KCl caused marked depression of salivary secretion in all experiments whereas infusion of NaCl had no consistent effect on flow. Intravenous infusion of KCl into the intact conscious sheep caused a slight depression of salivary secretion but minimum flow was significantly higher than that during intracarotid infusion. When the sheep were anaesthetized salivary flow rates were low and contralateral intracarotid infusion of KCl either had no effect on flow or caused an increase in flow. After ipsilateral cervical sympathectomy contralateral intracarotid infusion of KCl into the conscious sheep caused a marked depression of salivary flow similar to that occurring when the sheep were intact. After section of the secretomotor nerve of the gland salivary flow rates were low and contralateral intracarotid infusion of KC1 had no effect on flow. The salivary flow responses of the sheep were consistent, regardless of whether the KCl infusions were given within 24 h or 1-2 weeks after cervical sympathectomy or secretomotor nerve section. Salivary sodium concentration was negatively correlated with salivary flow in all experiments. It was concluded that potassium acted at a site located in the head but by direct action on the salivary gland. The depression of salivary secretion by hyperkalaemia resulted from a decline in neural activity in the parasympathetic secretomotor innervation of the parotid gland.     

Organic phosphate probes of the avian renal phosphate secretory mechanism

Parathyroid hormone (PTH) stimulates net renal inorganic phosphate (Pi) secretion in domestic fowl (Gallus domesticus). Recent evidence indicates that secreted Pi is derived from a highly sequestered, presumably organic, phosphate pool. A modified Sperber technique was used to survey the response of domestic fowl to unilateral renal portal infusions of organic phosphate compounds that had been implicated in previous studies of Pi secretion. None of the organic phosphate compounds produced a significant unilateral Pi secretory effect. It is concluded that these compounds neither directly stimulate Pi secretion in normal or parathyroidectomized birds, nor are they rate-limiting for the Pi secretory mechanism in birds infused with PTH.     

Active phosphate transport across the urinary bladder of the toad, Bufo marinus.

Net transport of inorganic phosphate occurs in the absence of an electrochemical gradient from the mucosal to the serosal bathing solution in the isolated toad urinary bladder. This transport can be inhibited by metabolic inhibitors. The magnitude of this transport can be altered by changes in phosphate concentration or by the addition of parathyroid hormone.     

性别及日龄对转人神经生长因子基因小鼠唾液中蛋白分泌的影响

神经生长因子(Nerve growth factor,NGF)是一种能促进神经元发育、分化、再生的蛋白。为高效生产药效更佳的人源NGF (hNGF)药物,最近,笔者实验室构建出唾液腺特异表达hNGF的转基因小鼠,并从该转基因小鼠唾液中纯化获得具有高生物学活性的h NGF蛋白。为了选择性别和日龄最适宜的转hNGF基因小鼠用于收集纯化hNGF蛋白,文中比较了28日龄(性成熟前)雄性、雌性,63日龄(性成熟后)雄性、雌性转hNGF基因小鼠,共4组转hNGF基因小鼠分泌的唾液量、唾液总蛋白量、唾液鼠源NGF (mNGF)蛋白量和唾液h NGF蛋白量等指标。结果显示,63日龄的转hNGF基因小鼠分泌的唾液量、唾液总蛋白量、唾液mNGF蛋白量和唾液hNGF蛋白量显著高于28日龄同一性别的转hNGF基因小鼠,且63日龄的雄性转hNGF基因小鼠分泌的唾液hNGF蛋白量显著高于同一日龄的雌性转hNGF基因小鼠;在4组小鼠中,63日龄的雄性转hNGF基因小鼠分泌的唾液hNGF含量最高,比28日龄雌性转hNGF基因小鼠高出约46倍,最适宜用于收集唾液并从中纯化hNGF。     

The influence of parathyroidectomy upon calcium and phosphate homeostasis in adult sheep.

The absorption and secretion of Ca and PO4 were measured with the use of radioactive isotopes in 4 adult sheep before and after parathyroidectomy. Secretion of Ca and PO4 into the stomach and intestines was measured separately. Parathyroidectomy resulted in a negative balance for Ca and PO4 and an accompanying fall in plasma Ca and PO4 concentrations. In the case of PO4 this response was attributed primarily to a reduced intestinal absorption, but for Ca increases in urinary excretion and intestinal secretion also contributed significantly. Secretion of PO4 to the stomach was reduced but endogenous PO4 excretion in the faeces was unchanged which indicated a reduced reabsorption of secreted PO4 by the intestines.     

Suppression of secondary hyperparathyroidism in uraemia: acute and chronic studies.

A study was conducted evaluating the response of serum parathyroid hormone to acute hypercalcaemia and long term administration of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in patients receiving maintenance haemodialysis. During infusion of elemental calcium 4 mg/kg/h over four hours in 12 patients not receiving vitamin D the concentration of serum amino terminal parathyroid hormone fell by 31-96% (mean 74.8 (SD 17.6)%) while that of carboxy terminal parathyroid hormone changed little. There was a strong inverse correlation between baseline serum calcium concentration and percentage fall in amino terminal parathyroid hormone during infusion (r = 0.88; p less than 0.001). In seven patients who received prolonged treatment with 1,25(OH)2D3 after calcium infusion there was a positive correlation between maximum percentage fall in amino terminal parathyroid hormone during infusion and the percentage fall in amino terminal parathyroid hormone after 1,25(OH)2D3 treatment (r = 0.79; p less than 0.05). The responsiveness of the parathyroid glands to changes in calcium in acute studies may be used to predict the efficacy of long term treatment with 1,25(OH)2D3. Patients in whom calcium infusion does not suppress parathyroid hormone may have true parathyroid autonomy and require early parathyroidectomy.     

The effects of acute phosphate depletion on isolated chick kidney tubule cells

Isolated tubule cells from chick kidney respond to a short period of phosphate deprivation with increased phosphate uptake and a resistance to parathyroid hormone. During phosphate depletion a considerable amount of phosphate may be released from the cells, but intracellular inorganic phosphate levels are maintained by the hydrolysis of organic phosphate esters. It is suggested that the concomitant changes in metabolism might act as the signal causing the onset of the changes in phosphate handling associated with phosphate deprivation.     

Acute regulation of parathyroid hormone by dietary phosphate

Secondary hyperparathyroidism in chronic renal failure is stimulated by dietary phosphate (P(i)) loading and ameliorated by dietary P(i) restriction. We investigated the rapidity of the response of serum parathyroid hormone (PTH) to changes in dietary P(i). When uremic rats adapted to a high P(i) diet (HPD) were fed a single meal of low P(i) diet (LPD), plasma PTH fell 80% within 2 h; plasma P(i) fell 1 mg/dl with no change in plasma ionized Ca (ICa). When uremic rats on the HPD were gavaged with LPD, PTH fell 60% within 15 min; plasma P(i) fell by 3.0 mg/dl with no change in total plasma Ca. However, HPD gavage increased PTH by 80% within 15 min with no change in plasma P or Ca, suggesting that the response may be independent of altered plasma P(i). Duodenal infusion of sodium P(i) increased PTH twofold within 10 min, with no change in ICa but an increase in plasma P(i), whereas duodenal infusion of NaCl had no effect on any of these parameters. Intravenous infusion of sodium phosphate also increased PTH within 10 min with no change in plasma ICa; intravenous NaCl had no effect. Additionally, duodenal infusion of phosphonoformate, a nonabsorbable phosphate analog, increased PTH fourfold within 5 min, but did not change plasma P or ICa. These findings indicate that oral P(i) increases PTH release in vivo more rapidly than previously reported; this response may be from both plasma phosphate and an additional signal arising from the gastrointestinal tract.     

Active phosphate transport across the urinary bladder of the toad,Bufo marinus

Summary Net transport of inorganic phosphate occurs in the absence of an electrochemical gradient from the mucosal to the serosal bathing solution in the isolated toad urinary bladder. This transport can be inhibited by metabolic inhibitors. The magnitude of this transport can be altered by changes in phosphate concentration or by the addition of parathyroid hormone.This work was presented in part at the Fall Meeting of the American Physiological Society Proceedings, October, 1975; Abstract inThe Physiologist, 1975,18:384.     

Metabolic clearance rate of adrenocorticotropin in the rat.

The metabolic clearance rate (MCR) of adrenocorticotropin (ACTH) was estimated after the intravenous infusion of graded rates of the hormone (40-2560 muU/min per 100 g body weight) in rats pretreated with chlorpromazine, morphine, and Nembutal, a preparation which proved effective in blocking endogenous ACTH release. The hormone was infused over a period of 45 min, at which time the plasma ACTH concentration had reached a steady state. A specific and sensitive bioassay, based on the corticosterone production of dispersed adrenal cells, was used to measure the plasma ACTH concentration. With increasing infusion rates of ACTH, a threefold decrease in the MCR of ACTH was observed. Previous studies of our group have shown that the MCR of corticosterone increases as a function of the infusion rate of the steroid. It appears, therefore, that the metabolism of these two hormonal links of the hypothalamo-pituitary-adrenocortical axis vary in opposite fashions as a function of the secretion rate of the hormone.     

Treatment of Paget's Disease of Bone with Mithramycin

We report data from three patients with severe Paget''s disease of bone who were treated with mithramycin.Mithramycin infusion resulted in a fall in plasma calcium, phosphate, alkaline phosphatase, and urinary hydroxyproline excretion. There was an improvement in calcium and phosphorus balance in two of the three subjects studied. A pronounced or complete relief of bone pain occurred in all three.We suggest that mithramycin exerts its beneficial effect in Paget''s disease of bone by stimulating parathyroid hormone release. The parathyroid hormone released has a predominantly anabolic action on bone since its catabolic action is blocked by mithramycin, which inhibits bone resorption.     

Sodium-dependent phosphate co-transporters

The renal proximal tubular reabsorption of inorganic phosphate (Pi) mediated by sodium-dependent phosphate (Na+/Pi) co-transporters plays a critical role in the maintenance of Pi homeostasis. Two nonhomologous Na+/Pi co-transporters (type I and type II) have been identified in the renal cortex of various species. The role of the type I co-transporter in Pi regulation remains to be clarified. Type II co-transporters play a major role in the regulation of renal Pi reabsorption by dietary Pi and parathyroid hormone, which regulate the rapid endocytosis/exocytosis of the transporters. Type III Na+/Pi co-transporters, which are expressed in a wide variety of tissues and are regulated by changes in the Pi concentration, have recently been described. The presence of a novel Pi-regulating hormone called 'phosphatonin' has been postulated in studies of the mechanisms of X-linked hypophosphatemic rickets and oncogenic osteomalacia. The regulation of phosphatonin and Na+/Pi co-transporters may provide novel pharmacological approaches to the treatment of these diseases.     

Alkaline phosphatase activity in whitefly salivary glands and saliva

Alkaline phosphatase activity was histochemically localized in adult whiteflies (Bemisia tabaci B biotype, syn. B. argentifolii) with a chromogenic substrate (5-bromo-4-chloro-3-indolylphosphate) and a fluorogenic substrate (ELF-97). The greatest amount of staining was in the basal regions of adult salivary glands with additional activity traced into the connecting salivary ducts. Other tissues that had alkaline phosphatase activity were the accessory salivary glands, the midgut, the portion of the ovariole surrounding the terminal oocyte, and the colleterial gland. Whitefly nymphs had activity in salivary ducts, whereas activity was not detected in two aphid species (Rhodobium porosum and Aphis gossypii). Whitefly diet (15% sucrose) was collected from whitefly feeding chambers and found to have alkaline phosphatase activity, indicating the enzyme was secreted in saliva. Further studies with salivary alkaline phosphatase collected from diet indicated that the enzyme had a pH optimum of 10.4 and was inhibited by 1 mM cysteine and to a lesser extent 1 mM histidine. Dithiothreitol, inorganic phosphate, and ethylenediaminetetraacetic acid (EDTA) also inhibited activity, whereas levamisole only partially inhibited salivary alkaline phosphatase. The enzyme was heat tolerant and retained approximately 50% activity after a 1-h treatment at 65 degrees C. The amount of alkaline phosphatase activity secreted by whiteflies increased under conditions that stimulate increased feeding. These observations indicate alkaline phosphatase may play a role during whitefly feeding.     

Sorting of transgenic secretory proteins in miniature pig parotid glands following adenoviral-mediated gene transfer

BACKGROUND: Gene transfer to salivary glands for use in treating both systemic and upper gastrointestinal tract diseases shows considerable potential. Numerous studies in rodents demonstrate that salivary glands can secrete transgenic secretory proteins either into saliva, primarily via the regulated secretory pathway (RSP), or into the bloodstream, primarily by the constitutive secretory pathway (CSP). The purpose of the present study was to assess the sorting characteristics of human growth hormone (hGH), a RSP protein, and human erythropoietin (hEpo), a CSP protein, in a large animal model of salivary gland gene transfer, the miniature pig. METHODS: Recombinant serotype 5 adenoviral (Ad5; 10(11) particles/gland) vectors encoding either hGH (AdCMVhGH) or hEpo (AdCMVhEpo) were administered to both parotid glands of male miniature pigs by intraductal cannulation. The secretion of hGH or hEpo was measured in both saliva and serum on days 3, 7 and 14 following administration. Detailed serum chemistry and hematological analyses were performed, and the presence of serum antibodies to hGH and hEpo was measured. For AdCMVhEpo-treated minipigs vector distribution in multiple tissues was determined by quantitative polymerase chain reaction (QPCR). RESULTS: The RSP protein hGH was secreted entirely into saliva, while the CSP protein hEpo was secreted into both saliva and serum. Most hEpo was found in saliva, but serum hEpo levels were sufficient to significantly increase hematocrit levels in treated animals by approximately 10%. Expression of both transgenes was maximal on day 3 and declined to near background by day 14. The amount of vector found in the targeted glands was 100 x more than in other tissues. CONCLUSIONS: Secretion of transgenic hGH from minipig parotid glands occurred principally into saliva via the RSP, as seen in rodents, while hEpo was secreted into both saliva and serum, the latter presumably via the CSP. Even though hEpo secretion into the bloodstream was not to the extent previously observed in rodents, serum hEpo levels were considerable and the hEpo was biologically active. Ad5 vector distribution was highly restricted to the parotid glands with little vector detected elsewhere. While the results in this large animal model support the established notion that salivary gland gene transfer can be used for treating systemic single protein deficiency disorders, they also highlight differences in transgenic CSP protein sorting between rodents and miniature pigs.     

Salivary acinar cells from aquaporin 5-deficient mice have decreased membrane water permeability and altered cell volume regulation

Aquaporins (AQPs) are channel proteins that regulate the movement of water through the plasma membrane of secretory and absorptive cells in response to osmotic gradients. In the salivary gland, AQP5 is the major aquaporin expressed on the apical membrane of acinar cells. Previous studies have shown that the volume of saliva secreted by AQP5-deficient mice is decreased, indicating a role for AQP5 in saliva secretion; however, the mechanism by which AQP5 regulates water transport in salivary acinar cells remains to be determined. Here we show that the decreased salivary flow rate and increased tonicity of the saliva secreted by Aqp5(-)/- mice in response to pilocarpine stimulation are not caused by changes in whole body fluid homeostasis, indicated by similar blood gas and electrolyte concentrations in urine and blood in wild-type and AQP5-deficient mice. In contrast, the water permeability in parotid and sublingual acinar cells isolated from Aqp5(-)/- mice is decreased significantly. Water permeability decreased by 65% in parotid and 77% in sublingual acinar cells from Aqp5(-)/- mice in response to hypertonicity-induced cell shrinkage and hypotonicity-induced cell swelling. These data show that AQP5 is the major pathway for regulating the water permeability in acinar cells, a critical property of the plasma membrane which determines the flow rate and ionic composition of secreted saliva.