Pertussis toxin-sensitive airway beta-adrenergic dysfunction by somatostatin

Area of Science:

• Pharmacology
• Respiratory Physiology
• Molecular Biology

Background:

• Airway smooth muscle relaxation is primarily mediated by beta-adrenergic stimulation.
• Somatostatin is a peptide hormone with diverse physiological roles.
• The precise mechanism of somatostatin's influence on airway beta-adrenergic function remains unclear.

Purpose of the Study:

• To investigate the effect of somatostatin on canine airway smooth muscle beta-adrenergic function.
• To elucidate the mechanism by which somatostatin modulates airway smooth muscle relaxation.

Main Methods:

• Isometric tension studies on canine bronchial smooth muscle in vitro.
• Dose-response curves for salbutamol, forskolin, dibutyryl cyclic AMP, verapamil, and nitroprusside.
• Measurement of intracellular cyclic adenosine monophosphate (cAMP) accumulation.
• Use of somatostatin antagonist and pertussis toxin to probe signaling pathways.

Main Results:

• Somatostatin (10(-6) M) significantly inhibited salbutamol-induced relaxation in a dose-dependent manner.
• Relaxant responses to forskolin were inhibited, but responses to dibutyryl cyclic AMP, verapamil, and nitroprusside were unaffected.
• Somatostatin suppressed salbutamol-induced intracellular cAMP accumulation.
• Inhibitory effects were abolished by a somatostatin antagonist and pertussis toxin.

Conclusions:

• Somatostatin down-regulates beta-adrenergic function in airway smooth muscle.
• This effect is mediated via activation of an inhibitory guanine nucleotide-binding regulatory protein (Gi) coupled to adenylate cyclase.
• Somatostatin represents a potential target for modulating airway smooth muscle tone.