The isolation and characterization of estrogen binding proteins in the pancreas of male and female hamsters

Abstract

Specific estradiol binding proteins (EBP) that have been described in the pancreatic tissues of a number of species are thought to be important in maintaining the structural and functional integrity of the pancreas. However, possible sex-related differences in the presence and characteristics of EBP have not been examined. In the present study, we have analyzed the pancreatic tissues of male and female Syrian golden hamsters for the presence of EBP and progesterone binding protein (PBP), and further characterized these sites. Our results indicate the presence of only one class of EBP with a high capacity (greater than 500 fmol/mg protein) and low affinity (Kd greater than 1.0 nM) in the pancreatic cytosol of female hamsters. On the other hand, there appeared to be two distinct classes of EBP in the male pancreas. One class of EBP in the male pancreas had a high binding affinity (Kd = less than 0.05 nM) and low capacity (less than 10 fmol/mg protein); we have arbitrarily called these Type I EBP. The second class of EBP in the male pancreas which resembled EBP in the female pancreas had a high capacity (greater than 100 fmol/mg protein) and a low binding affinity (Kd = greater than 1.0 nM); we have called these Type II EBP. The sucrose-density gradient profile of EBP for male and female hamster pancreas demonstrated the presence of both an 8S binding protein and a 4S binding protein in the male pancreas; the female pancreas had only a 4S binding protein. PBP were not detected in pancreas of either male or female hamsters. We conclude that significant sex-related differences are present in the EBP populations of the hamster pancreas.