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At least 253 records · Page 14Linked to original sources
PubMed1988

The role of HCO3- and Na+/H+ exchange in the response of rat parotid acinar cells to muscarinic stimulation.

The intracellular pH (pHi) of a rat parotid acinar preparation was monitored using the pH-sensitive fluorescent dye, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Under resting (unstimulated) conditions both Na+/H+ exchange and CO2/HCO3- buffering contribute to the regulation of pHi. Muscarinic stimulation (carbachol) of the acini produced a gradual rise in pHi (approximately 0.1 unit by 10 min) possibly due to activation of the Na+/H+ exchanger. When the exchanger was blocked by amiloride or sodium removal, carbachol induced a dramatic (atropine inhibitable) decrease in pHi (approximately 0.4 pH unit with t1/2 approximately 0.5 min at 1 mM carbachol). The rate of this acidification was reduced by removal of exogenous HCO3- and by the carbonic anhydrase inhibitor methazolamide. Also, acini stimulated with carbachol in Cl- -free solutions showed a more pronounced acidification than in the corresponding Cl- -replete media. Taken together, these data indicate that the carbachol-induced acidification of rat parotid acinar cells unmasked by inhibition of the Na+/H+ exchanger is due to a rapid loss of intracellular HCO3-. Carbachol induced acidification was inhibited by the Cl- channel blocker diphenylamine 2-carboxylate but not by 4-acetomido-4'-isothiocyanostilbene-2,2'-disulfonic acid, an inhibitor of Cl-/HCO3- exchange. In addition, this acidification could not be sustained in Ca2+-free media and was totally blocked by chelation of intracellular Ca2+. Interpreted in terms of HCO3- loss, these results closely parallel the pattern of carbachol-induced Cl- release from this same preparation and indicate that HCO3- is secreted in response to muscarinic stimulation via the same or a very similar exit pathway, presumably an apical anion channel. Under normal physiological conditions the intracellular acidification resulting from HCO3- secretion is buffered by the Na+/H+ exchanger.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1986

Hydrolysis of 4-nitrophenyl acetate catalyzed by carbonic anhydrase III from bovine skeletal muscle.

We report three experiments which show that the hydrolysis of 4-nitrophenyl acetate catalyzed by carbonic anhydrase III from bovine skeletal muscle occurs at a site on the enzyme different than the active site for CO2 hydration. This is in contrast with isozymes I and II of carbonic anhydrase for which the sites of 4-nitrophenyl acetate hydrolysis and CO2 hydration are the same. The pH profile of kcat/Km for hydrolysis of 4-nitrophenyl acetate was roughly described by the ionization of a group with pKa 6.5, whereas kcat/Km for CO2 hydration catalyzed by isozyme III was independent of pH in the range of pH 6.0-8.5. The apoenzyme of carbonic anhydrase III, which is inactive in the catalytic hydration of CO2, was found to be as active in the hydrolysis of 4-nitrophenyl acetate as native isozyme III. Concentrations of N-3 and OCN- and the sulfonamides methazolamide and chlorzolamide which inhibited CO2 hydration did not affect catalytic hydrolysis of 4-nitrophenyl acetate by carbonic anhydrase III.

Animals↗
PubMed1985

On the pharmacology of L-645,151: a topically effective ocular hypotensive carbonic anhydrase inhibitor.

L-645,151 [(2-sulfamoyl-6-benzothiazolyl)-2,2-dimethylpropionate] is the O-pivaloyl ester of L-643,799 (6-hydroxybenzothiazole-2-sulfonamide), topically administered L-645,151 being a substrate for ocular esterases with the resultant liberation of the active moiety, L-643,799, during penetration of the ocular surface. The minimum concentrations of topically administered suspensions (1 drop of 50 microliters into both eyes) of L-645,151, L-643,799, dichlorphenamide and methazolamide significantly lowering the elevated intraocular pressure (IOP) of the alpha-chymotrypsinized rabbit eye were 0.25, 2, 10 and 5%, respectively. IOP was not significantly decreased by 10% suspensions of acetazolamide or ethoxzolamide. The IOP lowering action of L-645,151 was local as the unilateral instillation of L-645,151 (0.25%) into the contralateral eye was devoid of effect in alpha-chymotrypsinized rabbits. L-645,151 (2%) decreased aqueous humor inflow in both the conscious rabbit and the anesthetized dog. Outflow facility in the conscious rabbit was unaltered by a 10% suspension of L-645,151. Low peak levels (0.52 microgram/g) of L-643,799 were present in rabbit renal cortex after the instillation of L-645,151 (2%) into both eyes; this treatment did not induce diuresis in the conscious rabbit. The corresponding maximum concentration in the iris + ciliary body was 4.01 micrograms/g. These preclinical studies reveal that L-645,151 is the most potent, topically effective ocular hypotensive carbonic anhydrase inhibitor described to date.

Administration, Topical↗
PubMed1979

Sickled erythrocytes, hyphema, and secondary glaucoma: V. The effect of vitamin C on erythrocyte sickling in aqueous humor.

In vivo incubations of Hgb SC erythrocytes showed significantly more sickling in anterior chambers characterized by high concentrations of ascorbic acid than in anterior chambers with low concentrations of ascorbic acid (normal guinea pigs compared with scorbutic guinea pigs and normal guinea pigs compared with normal rats). Low concentrations of ascorbic acid, however, did not completely eliminate intracameral sickling. Because acetazolamide raises the concentration of aqueous humor ascorbate, it should be used with considerable discretion when treating hyphema and secondary glaucoma caused by sickle cells. Methazolamide may be more desirable.

Acetazolamide↗
PubMed1997

Renal and cerebrospinal fluid formation pharmacology of a high molecular weight carbonic anhydrase inhibitor.

To achieve selective inhibition of cytosolic and membrane-bound carbonic anhydrase (CA II and CA IV, respectively), we synthesized a polymer of molecular weight 3500 from polyoxyethylene bis acetic acid and aminobenzolamide. The new compound, designated F (for Florida) 3500, is stable, water soluble and nontoxic. It is excreted largely unchanged by glomerular filtration. The Ki at 37 degrees C against CA II is 0.14 microM and against CA IV 4.0 microM, some 20 times more than the parent aminobenzolamide and about three times more than acetazolamide or methazolamide. F 3500 does not penetrate red cells and is confined to extracellular fluid. Relations of dose to renal HCO3-excretion was studied by i.v. injection into rats. Peak effect was reached with 100 mg/kg, eliciting 40 mM HCO3- in urine; this is taken to be the effect of inhibiting CA IV. This compares to a peak of 103 mM HCO3- after 3 mg/kg aminobenzolamide, which agrees with previous data on other low molecular weight sulfonamides and defines the effect on CA II and CA IV. We conclude that both isozymes are necessary for normal full renal reabsorption of HCO3-. We studied the effect of perfusing F 3500 (100-4000 microM) through the ventriculo-cisternal system of rats on cerebrospinal fluid (CSF) formation. F 3500 was also given intravenously at 100 mg/kg. CSF formation was unaffected. Low MW sulfonamides by either route lowered CSF formation 30 to 50%. It appears either that membrane-bound enzyme (CA IV) is not accessible from the CSF or blood side or that it plays little or no role in CSF formation.

Animals↗
PubMed1964

CLINICAL TRIALS WITH AGENTS CURRENTLY USED IN THE MANAGEMENT OF VAGINITIS.

Results of treatment of 151 cases of vaginitis in patients attending a leukorrhea clinic were studied. The incidence of each type of vaginitis is recorded. Analysis of results of treatment with six compounds currently used in the therapy of vaginitis indicated that acetarsol or pimaricin compounds, with their broader spectra of activity, appeared to be most useful, prior to establishment of a definite diagnosis by means of cultures. Chlordantoin is an effective antifungal agent and is associated with a high percentage of "culture cures". Resistant cases should be investigated for diabetes mellitus, and many are aided by a low carbohydrate diet. Metronidazole was used only for resistant cases of trichomoniasis, with a cure rate of over 80% when both partners were treated simultaneously. Triple-sulfa vaginal cream was effective in over 80% of patients with nonspecific vaginitis; no cases of resistant bacterial infections were encountered. Dienestrol cream was effective in relieving the symptoms of atrophic vaginitis.

Anti-Bacterial Agents↗
PubMed2002

Management of essential tremor.

Essential tremor (ET) is the most prevalent tremor syndrome. It commonly affects the hands, head, voice, and other body parts. Appropriate management begins with correct diagnosis. Primidone and propranolol are the first-line medications for the treatment for ET, but several other medications may also provide benefit. In patients with medically refractory tremor, alternative therapies, including surgery or injections of botulinum toxin, may be considered.

Adrenergic alpha-Antagonists↗