Binding properties of the insulin receptor of human placenta under different conditions of incubation.

The effect of incubation temperature and media on insulin receptor has been investigated employing membranes (4,000 x g pellet; particulate receptor) and solubilized material (solubilized receptor) from normal human placenta. Particulate receptor concentration (Ro) and affinity (Ke) were seen to be affected by buffer employed in binding experiments, both at 24 degrees C as well as at 4 degrees C; solubilized receptor affinity, on the other hand, is affected by buffer at 24 degrees C but not at 4 degrees C and receptor concentration does not vary at either temperature. Solubilization induced an increase in receptor affinity or in receptor concentration depending upon the buffer used in binding experiments. Insulin binding increases at the lowest incubation temperature; this phenomenon is due entirely to the greater receptor affinity on both particulate and solubilized receptor. From these data it appears that buffers induce variations in binding properties of the human placenta insulin receptor, thus, at ths present state of our knowledge, no definite conclusions can be drawn on the effect of procedures, such as solubilization, on human placenta insulin receptor affinity and/or concentration.