enisoprost and Diarrhea

A series of acyclic omega chain conjugated diene analogues of enisoprost were synthesized and evaluated for gastric antisecretory and diarrheagenic activities in comparison to enisoprost and a previously identified cyclic dienyl analogue. Several novel approaches to the cuprate reagents involved in the synthesis of the series are described. From this SAR study, it appears that both the conjugated diene and the overall space filling characteristics of the omega chain are important components to the pharmacological profiles and selectivity of these compounds and that a cyclic structure is not required.

Topics: Alprostadil; Animals; Anti-Ulcer Agents; Diarrhea; Dogs; Female; Gastric Acid; Gastric Juice; Male; Molecular Structure; Rats; Structure-Activity Relationship

Prostaglandin E (PGE) receptors in canine small intestinal mucosal and muscle membrane preparations were labeled with [3H] PGE1. Saturable, high affinity binding of [3H] PGE1 was observed in both preparations. The density of binding sites (fmol/mg protein) was 39 for mucosal membranes and 60 for muscle membranes, with corresponding dissociation constants of 10.6 nM and 5.8 nM, respectively. [3H] PGE1 binding sites in both preparations showed stereospecificity and high affinity for natural PGE1 and PGE2, but not for I or F-type PGs. Synthetic PGEs such as misoprostol and enisoprost had lower affinity than PGE1 or PGE2. Several analogs of enisoprost bound weakly to the binding sites. A highly significant correlation (C.C. = 0.9) was demonstrated between mucosal and muscle binding potency for a series of enisoprost analogs. There was also a significant positive correlation between the receptor binding potency and rat diarrheagenic activity for these analogs. These results indicate that PGE receptors in canine intestinal mucosa and muscle can be directly studied with [3H] PGE1 binding. The mucosal and muscle PGE receptors may have similar ligand binding specificity. We speculate that these receptors are likely to be associated with the diarrheagenic activity of PGEs.

Topics: Alprostadil; Animals; Anti-Ulcer Agents; Diarrhea; Dogs; Intestine, Small; Male; Misoprostol; Molecular Structure; Rats; Receptors, Prostaglandin; Receptors, Prostaglandin E; Sensitivity and Specificity; Tritium

A series of delta 17 unsaturated cycloalkyl and cycloalkenyl analogues of enisoprost was synthesized to investigate the effects of omega chain unsaturation on gastric antisecretory activity and diarrheogenic side effects. Of these, the 17E, 18-cyclopentenyl analogue 5d displayed potent gastric antisecretory activity in dogs but very weak diarrheogenic properties in rats and is the most selective prostaglandin compound discovered in these laboratories. Structurally, 5d contains both a conjugated diene and tertiary allylic alcohol in the omega chain, and these chemical features impart some interesting oxidative and acid-catalyzed epimerization and allylic rearrangement reactivities, respectively.

Topics: Alprostadil; Animals; Anti-Ulcer Agents; Diarrhea; Dogs; Drug Design; Gastric Juice; Magnetic Resonance Spectroscopy; Molecular Structure; Oxidation-Reduction; Rats; Secretory Rate; Structure-Activity Relationship

By use of standard cuprate methodology, a series of 18-cycloalkyl analogues of enisoprost was prepared in an effort to impede omega chain metabolism and prolong duration of gastric antisecretory activity. An initial product of omega chain oxidation, the C-20 hydroxy analogue, was also synthesized for pharmacological comparison. The cyclopropyl, cyclobutyl, and cyclopentyl analogues were approximately one-fourth as potent as enisoprost in inhibiting gastric acid secretion, while the cyclohexyl and cycloheptyl analogues showed very weak activity, and the 20-hydroxy compound was inactive at a dose 100 times the ED50 of enisoprost. The cyclobutyl compound had a longer duration of antisecretory action than enisoprost and the other cycloalkyl analogues. The cycloalkyl analogues unexpectedly possessed low diarrheogenic activity in rats.

Topics: Alprostadil; Animals; Anti-Ulcer Agents; Diarrhea; Dogs; Female; Gastric Acid; Male; Rats; Structure-Activity Relationship

The synthesis and gastric antisecretory activities of the delta 4,5-cis, delta 4,5-trans, and 4,5-acetylenic analogues of 15-deoxy-16-hydroxy-16-methyl prostaglandin E1 methyl ester are described. The key step in the preparation of these compounds involved the stereospecific conjugate addition of a cuprate reagent to the appropriate cyclopentenones. Although the trans and acetylenic derivatives were weak inhibitors of gastric acid secretion, the cis olefin was more potent and longer acting than the saturated parent compound. Selectivity with respect to unwanted diarrheagenic effects was found to be improved over that of both the parent 16-hydroxy compound and the reference standards, (15S)-15-methyl- and 16,16-dimethylprostaglandin E2.

Topics: Animals; Diarrhea; Dogs; Female; Gastric Mucosa; Histamine; Isomerism; Male; Prostaglandins E, Synthetic; Rats