title: Consequences of inhibition of bumetanide metabolism in rodents on brain penetration and effects of bumetanide in chronic models of epilepsy.
abstract: The diuretic bumetanide, which acts by blocking the Na-K-Cl cotransporter (NKCC), is widely used to inhibit neuronal NKCC1, particularly when NKCC1 expression is abnormally increased in brain diseases such as epilepsy. However, bumetanide poorly penetrates into the brain and, in rodents, is rapidly eliminated because of extensive oxidation of its N-butyl sidechain, reducing the translational value of rodent experiments. Inhibition of oxidation by piperonyl butoxide (PBO) has previously been reported to increase the half-life and diuretic activity of bumetanide in rats. Here we studied whether inhibition of bumetanide metabolism by PBO also increases brain levels of bumetanide in rats, and whether this alters pharmacodynamic effects in the kindling model of epilepsy. Furthermore, we studied the effects of PBO in mice. Mice eliminated bumetanide less rapidly than rats (elimination half-life 47 min vs. 13 min). Pretreatment with PBO increased the half-life in mice to average values (70 min) previously determined in humans, and markedly elevated brain levels of bumetanide. In rats, the increase in plasma and brain levels of bumetanide by PBO was less marked than in mice. PBO significantly increased the diuretic activity of bumetanide in rats and, less effectively, in mice. In epileptic mice, bumetanide (with PBO) did not suppress spontaneous seizures. In the rat kindling model, bumetanide (with or without PBO) did not exert anticonvulsant effects on fully kindled seizures, but dose-dependently altered kindling development. These data indicate that PBO offers a simple means to enhance the translational properties of rodent experiments with bumetanide, particularly when using mice.
authors.affiliation: Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine, Bünteweg 17, Hannover, D-30559, Germany; Center for Systems Neuroscience, Hannover, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Töpfer
authors.forename: Kathrin
authors.initials: K
authors.lastname: Töllner
authors.forename: Claudia
authors.initials: C
authors.lastname: Brandt
authors.forename: Friederike
authors.initials: F
authors.lastname: Twele
authors.forename: Sonja
authors.initials: S
authors.lastname: Bröer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Löscher
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology; D002034:Bumetanide / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use*; D004232:Diuretics / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use*; D007608:Kainic Acid / Q000633:toxicity; D051379:Mice; D010882:Piperonyl Butoxide / Q000494:pharmacology / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use*; D013226:Status Epilepticus / Q000139:chemically induced / Q000188:drug therapy*
chemical_list: D000975:Antioxidants; D004232:Diuretics; D049994:Sodium Potassium Chloride Symporter Inhibitors; D002034:Bumetanide; D010882:Piperonyl Butoxide; D007608:Kainic Acid
keywords: blood-brain barrier; diuresis; epilepsy; kindling; piperonyl butoxide; seizures