Effects of the selective beta 2-adrenergic agonists, procaterole and terbutaline, on protein secretion by rat submandibular glands

Involvement of apical P2Y2 receptor-regulated CFTR activity in muscarinic stimulation of Cl(-) reabsorption in rat submandibular gland

Previously, we presented in vivo evidence for a physiological significance of cAMP-regulated CFTR Cl(-) channels in Ca(2+)-activated Cl(-) reabsorption in the ductal system of the rat submandibular gland. Here, we address the mechanism by which basal CFTR activation contributes to the transepithelial Cl(-) movement evoked by muscarinic stimulation. The Cl(-) concentration ([Cl(-)]) was increased in the final saliva from rat submandibular gland during pilocarpine stimulation when a small interfering RNA for CFTR or a specific CFTR inhibitor, CFTR(inh)-172, was injected retrogradely into the gland's own duct, indicating that basal CFTR activation is involved in Cl(-) reabsorption. Systemically administered propranolol failed to alter the [Cl(-)], suggesting little involvement of a beta-adrenergic pathway in the Cl(-) movement that occurs through basal CFTR activation. Intraductal injection of suramin (a nonspecific P2-receptor antagonist) increased the salivary [Cl(-)], indicating the existence of endogenous purinergic activation. Upon separate intraductal injection, ATP and a P2Y(2)-receptor agonist, UTP, decreased the salivary [Cl(-)] almost equipotently. CFTR(inh)-172 and suramin each prevented these effects, whereas 2',3'-O-(4-benzoylbenzoyl)-ATP (Bz-ATP), a P2X(7) agonist, had no specific effect. Pilocarpine stimulation evoked ATP secretion into the salivary fluid. Immunohistochemistry revealed the partial coexistence of CFTR and P2Y(2) receptors on the luminal surface of epithelial cells in the striated ducts of this gland. These results raise the possibility that muscarinic stimulation-induced Cl(-) reabsorption occurs through basal CFTR activity and that this is regulated by P2Y(2) receptors in the ductal epithelium via stimulation by ATP secreted into the salivary fluid.

Interaction between substance P and beta-adrenergic agonists in the modulation of the secretion of fluid and protein by the rat submandibular gland

The interactions between substance P and beta-adrenergic agonists such as isoprenaline, dobutamine and terbutaline in the control of the secretion of fluid and protein from the rat submandibular gland have been examined. Substance P elicited large volumes of saliva whereas isoprenaline, dobutamine and terbutaline elicited small volumes only. The secretion of fluid in response to substance P was markedly enhanced when substance P was administered in combination with isoprenaline or dobutamine but not when it was administered in combination with terbutaline. Isoprenaline elicited large amounts of protein, whereas substance P elicited small amounts. The secretion of protein in response to isoprenaline did not change when isoprenaline was administered in combination with substance P. The secretion of fluid and protein induced by substance P in combination with isoprenaline was antagonized by metoprolol and by spantide, but it was unaffected by pretreatment with ICI118551. These results suggest that in the rat submandibular gland stimulation of beta1-adrenoceptors but not of beta2-adrenoceptors potentiates the secretion of fluid that is induced by stimulation of tachykinin receptors, whereas stimulation of tachykinin receptors does not enhance the secretion of protein that is induced by stimulation of beta1-adrenoceptors.

Fluid and protein secretion by the submandibular glands of weanling rats in response to various agonists

Secretion of fluid and protein by the submandibular glands of 25-day-old rats was investigated by stimulation with 22 sialogogues classified into five categories, four cholinergic, five beta 1-, seven alpha 1- and three alpha 2-adrenergic, and three peptidergic, at optimal doses. For fluid secretion, cholinergic and peptidergic agonists were the most powerful, whereas the beta 1- and alpha 1-adrenoceptor agonists were the most effective for the concentration of protein among the five categories, except for methoxamine. For total output of protein, the beta 1- and alpha 1-adrenoceptor agonists and pilocarpine were the most powerful among the 22 agonists, except for methoxamine and norephedrine. Cholinergic, peptidergic and alpha 2-adrenergic agonists among the five categories were less effective for protein secretion, except for pilocarpine. For the specific activity of esteroprotease, methoxamine and oxymetazoline, as alpha-adrenoceptor agonists, were the most powerful among the 22 agonists. Thus fluid and protein secretion evoked from the submandibular glands of weanling rats in response to a wide variety of agonists are similar to those of adult rats.

The effects of p-octopamine on salivary flow rates and protein secretion by rat submandibular glands

The effects of p-octopamine injected i.v. and i.p on salivary flow rates and proteins secreted by the submandibular glands of rats were studied with and without various types of autonomic blockers at different doses, and with two enzyme inhibitors. The salivary flow rates and the amounts of protein secreted progressively increased with increasing doses injected both i.v. and i.p., whereas they were dramatically reduced with almost all autonomic blockers and disulfiram, a dopamine-beta-hydroxylase inhibitor. Salivation was completely abolished in response to p-octopamine in combination with metoprolol or phenoxybenzamine at high doses, and simultaneous injections of prazosin and propranolol. The concentration of protein in submandibular saliva in response to p-octopamine injected i.v. and i.p. was not dose-dependent and significantly increased with all of the alpha-blockers except yohimbine, and with atropine and disulfiram. The protease activity was dose-dependent but was reduced significantly with alpha-blockers except yohimbine and with two enzyme inhibitors. The alpha-type of protein was secreted in response to p-octopamine injected i.v. and i.p. at all doses except with the lowest dose i.p., which caused the beta-type to be secreted. The alpha-type was completely replaced by the beta-type with all alpha-blockers at all doses, except with yohimbine, but no change was observed with various types of beta-blockers, yohimbine, atropine, and two enzyme inhibitors. Thus, p-octopamine could stimulate both the alpha- and beta-adrenoceptors in the submandibular glands of rats.

The effects of tyramine on salivary flow rate and protein secretion by rat submandibular glands

The effects of different doses of p-tyramine injected i.v. and i.p. on salivary flow rates and proteins secreted by the submandibular glands of rats were studied with and without various types of autonomic blockers and two enzyme inhibitors. The salivary flow rates and the amounts of protein secreted progressively increased with increasing doses injected both i.v. and i.p., whereas they were dramatically reduced with all autonomic blockers except the lowest doses of beta-blockers, atropine, and yohimbine. Salivation in response to p-tyramine injected i.v. and i.p. was completely abolished by simultaneous injections of both prazosin and propranolol. The concentration of protein was not dose-dependent and was not reduced by yohimbine and phenoxybenzamine at almost all doses used. However, prazosin significantly increased the protein concentration. Protease activities were dose-dependent but were significantly reduced with alpha-blockers other than yohimbine, and with most beta-blockers. The proteins secreted in response to p-tyramine at all doses injected i.v. and i.p. were of the alpha-type except with the lowest dose injected i.p. However, the alpha-type was completely replaced by the beta-type in the presence of all alpha-blockers except yohimbine, but not with beta-blockers, atropine, or two enzyme inhibitors. Pargyline, a monoamine-oxidase inhibitor, but not disulfiram, a dopamine-beta-hydroxylase inhibitor, affected all parameters except the type of protein. Thus, p-tyramine may activate both the alpha 1- and beta 1-adrenoceptors in the submandibular glands of rats directly or indirectly.

The effect of adrenergic agonists and antagonists on the expression of proteins in rat submandibular and parotid glands

The present investigation was undertaken to study the effect of adrenoreceptor modulators on the expression of salivary proteins. Sprague-Dawley rats were treated for 10 consecutive days with adrenergic agonists isoproterenol, dobutamine, terbutaline, salbutamol, methoxyphenamine, or methoxamine. Antiserum to selected salivary proteins was used to compare the concentration of these proteins in the submandibular and parotid glands of treated animals. Chronic treatments of rats (50 mumol/kg body weight for 10 d) with either isoproterenol or dobutamine induced synthesis of a cysteine-proteinase inhibitor (cystatin) in the submandibular glands. When isoproterenol was injected concomitantly with the mixed beta-antagonist propranolol or the beta 1-adrenergic antagonists metaprolol, protocol, or atenolol, the induction of cystatin was totally suppressed. However, the beta 2-antagonist, ICI-118551, produced only partial reduction in cystatin induction elicited by isoproterenol. On the contrary, rats treated with either isoproterenol or beta 1-agonists demonstrated a significantly reduced concentration of serine-proteinase kallikrein in submandibular glands. The decrease observed in submandibular kallikrein of rats treated with isoproterenol was prevented by concomitant treatment with beta 1-antagonists but not with beta 2-antagonists. Because kallikreins are produced by ductal cells and cystatins are produced by acinar cells of submandibular glands, these observations suggest that there may be differential control of expression of proteins synthesized by ductal and acinar cells. Chronic treatment of rats with nonselective beta-agonist isoproterenol or beta 1-selective agonists increased markedly the proline-rich proteins (PRP) in parotid glands, but the parotid amylase concentration was not significantly affected by beta-adrenergic agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of m-octopamine on salivary flow rates and protein secretion by rat submandibular glands

1. m-Octopamine given i.v. or i.p. was a potent sialogogue for rat salivary glands. 2. Salivation in response to i.v. m-octopamine was completely abolished by prazosin and phenoxybenzamine. 3. The alpha-type of proteins were secreted in response to all doses of i.v. and i.p. m-octopamine and these were converted into the beta-type with prazosin, but not with yohimbine. 4. m-Octopamine stimulated both alpha- and beta-adrenoceptors and was a much more selective alpha 1-agonist than was the p-isomer.

The effect of adrenergic agonists and antagonists on cysteine-proteinase inhibitor (cystatin) in rat saliva

The effect of a number of adrenergic agonists and antagonists on the induction of rat salivary cystatin was investigated. A highly sensitive and specific radioimmunoassay was used to determine cystatin in rat whole saliva. Treatment for 10 consecutive days with a non-specific beta-adrenergic agonist isoproterenol, or the beta 1-adrenergic agonists dobutamine or methoxyphenamine, resulted in the induction of the salivary cystatin. Induction was also found in rats treated for 10 days with arterenol. Only trace quantities of cystatin could be detected in saliva of rats treated with the beta 2-adrenergic agonists terbutaline or salbutamol. When isoproterenol was injected concomitantly with the mixed beta-antagonist propranolol or the beta 1-adrenergic antagonists metaprolol, proctocol or atenolol the production of cystatin was totally suppressed. However, the beta 2-antagonist, ICI 118551, produced only a partial reduction in salivary cystatin induction elicited by isoproterenol. The findings suggest that the induction of salivary cystatin is regulated, in part, by beta 1-adrenergic receptor stimulation.

Chronic treatment with beta adrenergic agonists and antagonists alters the composition of proteins in rat parotid saliva

This investigation was undertaken to determine the role of beta-adrenergic receptors in the regulation of the protein composition of rat parotid saliva. Chronic treatment of rats with dobutamine, a beta 1-adrenergic agonist, resulted in changes in parotid saliva volume, protein concentration, and composition which were essentially the same as those changes which occurred following chronic treatment with isoproterenol, a non-specific beta-adrenergic agonist. Chronic treatment with the beta 2-adrenergic agonist, terbutaline, had no effect on parotid saliva volume, protein concentration, or composition. Chronic treatment of rats with a beta 1-adrenergic antagonist, metoprolol, had different effects on saliva dependent on the manner by which the drug was delivered. Twice-daily injections of metoprolol led to a decrease in flow rate, but protein concentration and composition were unaltered. When metoprolol was delivered by surgically implanted osmotic minipumps, neither the flow of parotid saliva nor its concentration of protein was altered; however, there was a reduction in the proportion of proline-rich proteins in saliva. Comparable changes in parotid saliva protein composition occurred when the minipumps delivered propranolol, a non-specific beta-adrenergic antagonist. Chronic treatment of rats with an alpha 2-adrenergic agonist (clonidine) or antagonist (yohimbine) was without effect on parotid saliva flow rate, protein concentration, or composition. These findings suggest that the synthesis of proline-rich proteins is regulated, in part, by beta-adrenergic receptor stimulation, and primarily by the beta 1-receptor subtype.

Autonomic effects on protein secretion by rat submandibular salivary glands

1. Following treatment with cholinergic and beta-adrenergic drugs, the beta-type protein, associated with cAMP, was secreted regardless of the doses used. 2. Following treatment with alpha 1-adrenergic drugs, both the beta-type and alpha-type proteins were secreted depending on the doses used and the alpha-type protein was completely converted to the beta-type with alpha-blockers. 3. Following treatment with alpha 2-adrenergic drugs, the gamma-type protein, associated with cGMP, was secreted independent of the doses used.