Hypothetical multiple forms of cytoplasmic ER and PgR and commentary remarks.

Based on the generalization from previous studies the hypothetical multiple forms of cytoplasmic ER and PgR are proposed. Eight forms of ER and 10 forms of PrR have been observed as a whole. However, only four forms of ER, monomer, dimer, tetramer and hexamer, and five forms of PrR, monomer A or B, dimer AB, tetramer AB . AB and hexamer 3(AB) of PgR commonly occur. In conclusion, comments on our results and on those of others are made. Previous studies (1,2) have demonstrated that the high polymeric forms of cytoplasmic ER and PrR from rabbit uteri contain major activity. In continuous studies (3,4) the solubilized nuclear ER and PgR from rabbit uteri demonstrated the similarity of multiple forms to the cytoplasmic receptors. Further, by analyses of human breast tumors (5) similar multiple forms in both cytoplasmic and nuclear ER and PrR have been revealed. In order to generalize what we have observed with our rational experimental approaches we are proposing hypothetical multiple forms of cytoplasmic ER and PrR in this communication.