Effects of thyrotropin-releasing hormone on pancreatic exocrine secretion in the dog.

Effects of thyrotropin-releasing hormone (TRH) on pancreatic exocrine secretion were investigated in isolated and blood-perfused canine pancreas preparations. During constant intra-arterial infusion of secretin (0.03-0.05 units/min), concentrations of protein and bicarbonate in the pancreatic juice were measured before and after intra-arterial injection of TRH (0.1-10 ng). TRH did not produce any significant changes in the flow rate of pancreatic juice and in the rate of pancreatic blood flow. TRH caused a significant suppression of protein and bicarbonate output in a dose-dependent manner. At 10 ng of TRH, this suppression lasted about 20 min. From these data, it is suggested that TRH acts directly on both acinar and ductular cells of the pancreas and inhibits the secretions of digestive enzymes and bicarbonate.