Lithocholyltaurine interacts with cholinergic receptors on dispersed chief cells from guinea pig stomach.

Although bile acids damage gastric mucosa, the mechanisms underlying tissue injury induced by these agents are not well understood. To determine whether bile acids alter gastric secretory function, we investigated the actions of sodium cholate, deoxycholate, lithocholate, and their taurine and glycine conjugates on a highly homogeneous population of gastric chief cells. Lithocholyltaurine (LCT), a particularly injurious bile acid, caused a threefold increase in pepsinogen secretion (detectable with 100 nM and maximal with 10 microM LCT). When combined with other secretagogues, increasing concentrations of LCT caused progressive inhibition of carbamylcholine (carbachol)-induced pepsinogen secretion but did not alter CCK- or 8-bromo-cAMP-induced secretion. Taurine and unconjugated lithocholate did not alter basal or carbachol-induced secretion. These observations suggested that LCT is a partial cholinergic agonist. To test this hypothesis, we examined the actions of the cholinergic antagonist atropine on LCT-induced pepsinogen secretion. Atropine (10 microM) abolished carbachol- and LCT-induced pepsinogen secretion. Likewise, carbachol (0.1 mM) and LCT (1 mM) induced an atropine-sensitive, two- to threefold increase in cellular levels of inositol 1,4,5-trisphosphate. We examined the actions of LCT on binding of the cholinergic radioligand [N-methyl-3H]scopolamine ([3H]NMS) to chief cells. Half-maximal inhibition of [3H]NMS binding was observed with approximately 0.5 mM carbachol and 1 mM LCT. These results indicate that the bile acid LCT is a partial agonist for muscarinic cholinergic receptors on gastric chief cells.

Identification of an aldose reductase inhibitor site by affinity labeling.

Animal studies indicate that aldose reductase inhibitors represent a pharmacological method for inhibiting the onset of diabetic complications that is independent of blood sugar control. This has spurred the development of aldose reductase inhibitors (ARIs). To facilitate the rational development of more potent and direct ARIs, more specific knowledge of the structural and pharmacophoric requirements of the site at which ARIs interact are required. Co-crystallization of human placental aldose reductase with the inhibitor zopolrestat has been reported to result in a complex where the inhibitor is almost completely sequestered in the hydrophobic pocket which forms the substrate site. Zopolrestat's observed location, which makes the active site pocket inaccessible to solvent or further productive binding of substrate, is not supported by published inhibitor structure-activity relationships (SAR) studies or kinetic results which indicate that aldose reductase inhibitors such as zopolrestat are either non-competitive or uncompetitive inhibitors. Using a 5-iodoacetamido analog of alrestatin as an affinity labeled aldose reductase inhibitor, an inhibitor binding site on aldose reductase has been located. This inhibitor binding site contains a number of pharmacophoric elements previously proposed for the inhibitor site. Its location and composition is consistent with reported kinetic data, SAR observations, stereochemical requirements, and quantum chemical calculations.

Synthesis and properties of new derivatives of ethyl 7-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrido [2,3-d]pyrimidine-5-carboxylate.

Condensation of diethyl 2-amino-6-methylpyridine-3,4-dicarboxylate with phenyl or cyclohexyl isocyanates gave the corresponding derivatives of ethyl 7-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrido [2,3-d]pyrimidine- 5-carboxylate[(V), (VI)]. Alkylation of (V) and (VI) afforded the corresponding N-1 substituted derivatives (XI-XIX).

Synthesis and properties of the derivatives of 2-alkylthio-4-oxo-3,4- (and -1,4)-dihydropyrido-[2,3-d]pyrimidine-5- and -6-carboxylic acids.

Condensation of diethyl 2-amino-6-methylpyridine-3,4-dicarboxylate (I) with the corresponding isothiocyanates afforded derivatives of ethyl 4-oxo-2-thioxo-1,2,3,4-tetrahydropyrido [2,3-d]pyrimidine-5-carboxylate (V-VII). Alkylation of (V), (VI) and (XI) gave the corresponding derivatives of ethyl 2-alkylthio-4-oxo-3,4-(and 1,4)-dihydropyrido[2,3-d]pyrimidine-5- and -6- carboxylate [(XII-XVI), (XX-XXII)]. Some of the obtained compounds were active pharmacologically.

Synthesis and properties of new 3-acyl- and 3-carbamoyl derivatives of esters of 3H-2-imino-7-methyl-4-oxopyrido[3,2-e]-1,3-thiazine-5- and -6-carboxylic acids.

It was stated that esters of 3H-2-imino-7-methyl-4-oxopyrido[3,2-e]-1,3-thiazine-5- and -6-carboxylic acids react with acyl anhydrides and chlorides giving 3-acyl derivatives. Reaction of the above mentioned esters with isocyanates affords the corresponding 3-carbamoyl derivatives.

Synthesis and properties of 3-aminomethyl derivatives of 3H-2-imino-7-methyl-4-oxopyrido-[3,2-e]-1,3-thiazine-5- and -6-carboxylic acids.

It was stated that esters of 3H-2-imino-7-methyl-4-oxopyrido [3,2-e]-1,3-thiazine-5- and -6-carboxylic acids (I, II) undergo the Mannich reaction giving the corresponding 3-aminomethyl derivatives (III-XIV). Derivatives of ester II [(XII) and (XIV)] showed distinct analgesic and antiserotonic activities.

Investigations on the synthesis and properties of new derivatives of pyrido[3,2-e]-1,3-thiazino[3,2-a]-s-triazine.

It has been found that the condensation of esters of 3H-2-imino-7-methyl-4-oxopyrido[3,2-e]-1,3-thiazine-5- and -6-carboxylic acids (I, II) with formaldehyde and primary amines affords the corresponding derivatives of a new heterocyclic system pyrido[3,2-e]-1,3-thiazino [3,2-a]-s-triazine (IX-XXIV).