Cross-desensitization to furosemide and salbutamol in isolated neonatal guinea pig airways.
Airway hyperresponsiveness in neonatal chronic lung disease is treated with both furosemide, a diurectic that inhibits the Na-K-2Cl cotrasporter, and salbutamol, a beta2-adrenoceptor agonist. Tachyphylaxis to both drugs in vitro has been described. This study was conducted to determine if the relaxation response in newborn guinea pig airways to furosemide and salbutamol can be cross-desensitized in vitro. Tracheal ring segments from 4- to 7-day-old guinea pigs were suspended in HEPES buffer for measurement of isometric tension. Segments were pre-treated with either furosemide (300 microM, 1 h) or salbutamol (10 microM, 30 min). After constriction with 3 microM acetylcholine, relaxation response to salbutamol or furosemide, respectively, was measured. Pretreatment with furosemide diminished relaxation response to salbutamol [87 +/- 3% (n = 11) vs. 117 +/- 8% (n = 10), p < 0.05], as compared to saline-treated controls. In addition, pretreatment with salbutamol diminished relaxation response to furosemide [53 +/- 2% (n = 11) vs. saline-treated (83 +/- 7%, n = 7, p < 0.05) and DMSO-treated controls (69 +/- 5%, n = 5, p < 0.05)]. Measurements of 86Rb uptake, cyclic AMP levels and responses in the presence of charybdotoxin make it unlikely that Na-K-2Cl cotransporter activity, stimulation of cAMP, or opening of maxi-K+ channels are mechanisms involved in the cross-desensitization to furosemide and salbutamol in vitro.
Department of Pediatrics, Kapiolani Medical Center for Women and Children and the John A. Burns School of Medicine, Honolulu, Hawaii 96826, USA.
R P
RP
Gelber
M J
MJ
Christ
L M
LM
Iwamoto
G A
GA
Marinkovich
N
N
Fujiwara
K T
KT
Nakamura
D000109:Acetylcholine / Q000494:pharmacology; D000420:Albuterol / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D004361:Drug Tolerance; D005665:Furosemide / Q000008:administration & dosage / Q000494:pharmacology*; D006168:Guinea Pigs; D007537:Isometric Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D012414:Rubidium Radioisotopes / Q000378:metabolism; D014132:Trachea / Q000187:drug effects* / Q000502:physiology
D001993:Bronchodilator Agents; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D005665:Furosemide; D000242:Cyclic AMP; D000109:Acetylcholine; D000420:Albuterol