Insulin receptor binding in pork brain: different affinities of porcine and human insulin.

The insulin receptor binding of human and pork insulin was measured in four different pork brain tissues. In medial hypothalamus, infundibulum of pituitary gland, neurohypophysis, and adenohypophysis insulin receptors were found. Binding of mono-125I-(TyrA14)-insulin proceeded rapidly at 37 degrees C, pH 7.4, and reached a steady state for human and pork insulin at 15 minutes. Biosynthetic human insulin and semisynthetic human insulin dissociated more rapidly than pork insulin. In the four tested brain tissues the specific insulin binding per mg protein differed significantly (2p less than 0.01). The receptor affinity constant of human insulin was significantly (2p less than 0.01) lower in comparison to pork insulin in the four brain tissues studied. This study demonstrates that there are insulin receptors in pork brain tissue, that the amounts of these receptors vary depending on the area and that the brain insulin receptors react differently to pork and human insulin.