Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043352 (xerostomia)
 4,250 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We used the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6')-carboxyfluorescein to monitor the recovery of the intracellular pH (pHi) of rat parotid acini from an NH4(+)-induced alkaline load. This recovery was markedly inhibited by the loop diuretic bumetanide and by Cl- removal, indicating that it is largely due to NH4+ entry via the basolateral Na(+)-K(+)-2Cl- cotransporter. The rate of recovery of pHi was enhanced threefold by pretreatment (37.5 s) with isoproterenol (K1/2 = 21.5 nM) or norepinephrine (in the presence of phentolamine), and blocked by the beta 1-specific antagonist atenolol, indicating an upregulation of cotransport activity by beta 1-adrenergic stimulation. The effect of isoproterenol was prevented by protein kinase inhibitors and mimicked by cAMP analogues, and by maneuvers known to increase cytosolic cAMP levels in these cells, consistent with the involvement of protein kinase A. Physiologically, such an upregulation of the acinar Na(+)-K(+)-2Cl- cotransporter would lead to an increase in acinar chloride uptake across the basolateral membrane, and consequently, an increase in overall chloride and fluid secretion. Prevention of this upregulation by beta-blockers and possibly by other commonly used clinical agents may account for the dry mouth and dry eyes experienced by some patients taking these medications.
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PMID:Beta-adrenergic upregulation of the Na(+)-K(+)-2Cl- cotransporter in rat parotid acinar cells. 131 47

Muscarinic receptor antagonists (antimuscarinics) serve as the cornerstone in the pharmacological management of overactive bladder (OAB) by relieving the symptoms of urgency, frequency and incontinence. These drugs operate primarily by antagonizing post-junctional excitatory muscarinic receptors (M(2)/M(3)) in the detrusor. The combination of pharmacological and gene knockout studies has greatly advanced our understanding of the functional role of muscarinic receptors in the bladder. M(3) receptors produce direct smooth muscle contraction by a mechanism that relies on entry of extracellular calcium through L-type channels and activation of a rho kinase. M(2) receptors, which predominate in number, appear to facilitate M(3)-mediated contractions. M(2) receptors can also produce bladder contractions indirectly by reversing cAMP-dependent beta-adrenoceptor-mediated relaxation, although the physiological role of beta-adrenoceptors in detrusor relaxation is controversial. Emerging evidence suggests that muscarinic receptors in the urothelium/suburothelium can modulate the release of certain factors, which in turn may affect bladder function at the efferent or afferent axis. Currently, oxybutynin, tolterodine, darifenacin, solifenacin and trospium are the five major antimuscarinics approved for the treatment of OAB. Comparative clinical studies have shown that oxybutynin and solifenacin may be marginally more effective than tolterodine, although the latter seems to be better tolerated. Pharmacokinetic-pharmacodynamic analyses using plasma concentrations of 'total drug' indicate that, at therapeutic doses, the clinical efficacy of darifenacin and solifenacin may be driven primarily by selective M(3) receptor occupation, whereas the pharmacodynamic effects of pan-selective molecules (such as tolterodine, trospium) may potentially involve multiple receptors, including M(2) and M(3). Furthermore, high M(3) receptor occupation is the likely explanation for the greater propensity of darifenacin and oxybutynin to cause dry mouth and/or constipation. Although the recently introduced drugs represent a significant improvement over older drugs, especially with respect to the convenience of dosing schedule, their overall efficacy and tolerability profile is still less than optimal and patient persistence with therapy is low. Recent advances in basic research have not yet offered a clear discovery path for improving the therapeutic index of antimuscarinic molecules. There is still an unmet need for an antimuscarinic medicine with superior clinical effectiveness that can translate into better persistence on therapy.
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PMID:Muscarinic receptors in the bladder: from basic research to therapeutics. 1646 86