The Effect of Alpha- and Beta-Adrenergic Agonists and Blockers on Postprandial Pancreatic Polypeptide Release in Dogs

Abstract

The influence of adrenergic agonists—phenylephrine (alpha), isoproterenol (beta), and salbutamol (beta₂)—and of adrenergic blockers—phentolamine (alpha), propranolol (beta), and practolol (beta₁)—on the postprandial pancreatic polypeptide (PP) release has been assessed in five Labrador retrievers. Infusions of phenylephrine, 0.12 mg kg⁻¹h⁻¹; isoproterenol, 3 μg kg⁻¹h⁻¹; salbutamol, 12 μg kg⁻¹h⁻¹, did not significantly affect PP release. Propranolol, 0.5 mg kg⁻¹, and propranolol, 0.5 mg kg⁻¹, + phentolamine, 1 mg kg⁻¹, combined, given as intravenous boluses before the meal significantly reduced PP release (44% and 58% of controls, p < 0.05), whereas phentolamine, 1 mg kg⁻¹, and practolol, 1 mg kg⁻¹, had no effect. Phenylephrine combined with phentolamine and isoproterenol combined with propranolol and practolol did not influence PP secretion. It is concluded that the postprandial PP release is stimulated by beta₂-adrenergic mechanisms.

Key-words:

• Isoproterenol
• pancreatic polypeptide
• phentolamine
• phenylephrine
• practolol
• propranolol
• salbutamol