Pancreatic endocrine responses to exogenous neurotensin in the conscious calf.

1. Responses to neurotensin have been investigated in conscious calves 2-5 weeks after birth given continuous I.V. infusions of the peptide for 15 min (5 pmol. kg-1 . min-1). 2. In control calves the concentration of the peptide in the arterial plasma had risen by 160 +/- 10 pmol/l at the end of the infusion,. after which it fell exponentially (t1/2: 1.4 min). 3. This dose of neurotensin produced no significant change in mean heart rate, aortic blood pressure, plasma gastrin or glucose concentration. 4. It was found that neurotensin could produce a pronounced rise in the concentration of both insulin and pancreatic polypeptide (PP) in the arterial plasma, together with a much smaller rise in pancreatic glucagon concentration. 5. Each of these three pancreatic endocrine responses was found to be glucose-sensitive within the range ca. 5.0-9.0 mmol/l. Hyperglycaemia potentiated insulin release and inhibited release of PP and glucagon. 6. The results are discussed in relation to the findings of other workers in other species.