Extracellular ATP regulation of feline tracheal submucosal gland secretion
Shimura, S.; Sasaki, T.; Nagaki, M.; Takishima, T.; Shirato, K.
American Journal of Physiology 267(2 Pt 1): L159-L164
1994
ISSN/ISBN: 0002-9513 PMID: 8074238 Document Number: 431319
The standard patch-clamp technique was employed on enzymatically digested acinar cells of submucosal glands isolated from feline trachea. ATP (- 10-3 M) evoked bidirectional current responses and an initial inward current at -80 mV (Cl- current) was followed by an outward current at 0 mV of membrane potential (K+ current). Isoproterenol (ISO) alone did not evoke any significant current responses. However, ISO augmented the ATP-induced inward and outward currents. A phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, mimicked the augmentation by ISO. (Ca-2+)-i of acinar cells in isolated gland was measured using a fluorescent dye, fura 2. ATP (-10-3 M) induced an immediate increase in (Ca-2+)-i followed by a prolonged plateau, and Ca-2+ removal resulted in an initial increase alone without the prolonged phase. ISO also augmented the ATP-evoked increases in (Ca-2+)-i mainly in the plateau phases. Mucus glycoprotein (MGP) secretion was estimated by measuring trichloroacetic acid-precipitable (3H)glycoconjugates from isolated glands. ATP (-10-3 M) evoked significant MGP secretion and ISO enhanced the ATP-induced MGP secretion. In contrast, adenosine (-10-3 M) produced no significant responses in current, MGP secretion, or (Ca-2+)-i. These findings suggest that 1) P-2-receptor stimulation and the resultant (Ca-2+)-i rise induced both electrolyte and MGP secretions and 2) ATP-induced secretion is enhanced by an adenosine 3',5'cyclic monophosphate intracellular concentration (cAMP)-i-rise after beta-receptor stimulation in airway submucosal glands.