Exacerbation of acetazolamide teratogenesis by amiloride and its analogs active against Na+/H+ exchangers and Na+ channels.

Abstract

Postaxial forelimb ectrodactyly induced by acetazolamide given on Day 9.5 of murine gestation is thought to be mediated by reduced intracellular pH (pHi) within the limb bud. Coadministration of amiloride increases the incidence and severity of acetazolamide-induced forelimb malformations and further reduces limb bud pHi. These findings were hypothesized to be attributable to the action of amiloride as an inhibitor of Na+/H+ exchangers (NHEs), plasma membrane-localized proteins involved in the maintenance of cellular pH homeostasis. Here, we explored this hypothesis further by coadministering with acetazolamide, amiloride, or analogs known to preferentially inhibit NHEs 5-(N-methyl-N-isobutyl)-amiloride, 5-(N, N-hexamethylene)-amiloride, 5-(N, N-dimethyl)-amiloride, and 5-(N-ethyl-N-isopropyl)-amiloride or amiloride-sensitive Na+ channels (benzamil). The coadministration of either amiloride, benzamil, 5-(N, N-dimethyl)-amiloride, 5-(N-ethyl-N-isopropyl)-amiloride, or 5-(N-methyl-N-isobutyl)-amiloride all dose responsively increased the frequency and severity of forelimb malformations compared to acetazolamide alone. None of the analogs given alone induced forelimb ectrodactyly. The data are consistent with the original hypothesis that the exacerbation of acetazolamide teratogenesis is due to NHE inhibition. Surprisingly, benzamil was the most potent potentiator of acetazolamide teratogenesis. This result strongly suggests that amiloride-sensitive Na+ channels are also present within the murine embryo and are likely to play a role in pHi homeostasis.

• Authors: S M Bell, C M Schreiner, E Resnick, C Vorhees, W J Scott Jr
• Journal: Reproductive toxicology (Elmsford, N.Y.) (Reprod Toxicol) 1997 Nov-Dec Vol. 11 Issue 6 Pg. 823-31 ISSN: 0890-6238 [Print] United States
• PMID: 9407593 (Publication Type: Journal Article)

Chemical References

• Carbonic Anhydrase Inhibitors
• Sodium Channel Blockers
• Sodium-Hydrogen Exchangers
• Amiloride
• Acetazolamide

Topics

• Abnormalities, Drug-Induced (etiology)
• Acetazolamide (toxicity)
• Amiloride (toxicity)
• Animals
• Carbonic Anhydrase Inhibitors (toxicity)
• Drug Synergism
• Female
• Mice
• Mice, Inbred C57BL
• Pregnancy
• Sodium Channel Blockers
• Sodium-Hydrogen Exchangers (antagonists & inhibitors)