Human and
porcine insulin were administered intravenously to a group of healthy volunteers in two different doses (0.075 IU/kg
body weight and 0.12 IU/kg
body weight) and to two groups of randomly selected patients with
pituitary disorders in a dose adapted to their individual
glucose tolerance (0.12-0.17 IU/kg
body weight for porcine and 0.15-0.18 IU/kg
body weight for human
insulin). The
blood glucose and
potassium lowering effect, the feedback regulation of endogenous
insulin release, and the liberation of the counterregulatory
hormones glucagon,
cortisol,
adrenocorticotropic hormone (
ACTH),
prolactin (hPRL),
human growth hormone (hGH), and
catecholamines were measured before and after injection of human or
porcine insulin. The maximal effect, the area under the concentration-time curve, the percentage effect, and the increase above baseline for the two doses of
insulin and the two types of
insulin were compared. There were no significant differences in the calculated parameters between the two
insulin types at the same doses except with
prolactin. At 0.075 IU/kg human
insulin induced significantly less
prolactin release than
porcine insulin. Comparing the two doses of the same
insulin serum
insulin levels,
blood glucose,
glucagon,
norepinephrine, and
prolactin were lower at the low dose of each
insulin. In addition
ACTH and
epinephrine were also lower after human
insulin at 0.075 IU/kg. The subjective signs of
hypoglycemia were less pronounced after human
insulin. It is concluded that the
biological effects of human
insulin are comparable to
porcine insulin although
prolactin release is significantly reduced after human
insulin. If this difference is an indication of different receptor sensitivities for human and
porcine insulin in the central nervous system and if the diminished signs of
hypoglycemia are a consequence of this, then further studies are required.