Humoral and cardiovascular responses to feeding in pigs.

In young pigs, allowed to feed after various periods of food deprivation, the changes in plasma levels of insulin, glucose, and corticosteroids were measured. Food was presented in bowls or obtained by operant response. In pigs deprived of food for 17 h there was a marked rise in insulin from 15 +/- 1 to 91 +/- 10 microU/ml and glucose from 94 +/- 2 to 112 +/- 4 mg/dl when feeding began, while the corticosteroid levels were reduced from 48 +/- 8 to 29 +/- 9 ng/ml. Evidence for a cephalic phase of insulin secretion was seen in 17-h fasted pigs. In pigs fed ad libitum there were no significant changes in the levels of insulin, glucose, or corticosteroids. The changes observed in the 5-h fasted pigs were intermediate. No differences were seen between bowl-fed and operant pigs. Pressure transducers were surgically implanted in the carotid arteries of three pigs. When 17-h fasted pigs started to eat there was a marked rise of blood pressure from 114 +/- 3 to 147 +/- 5 mmHg and a similar increase was seen when satiated pigs drank milk.