The effect of sodium molybdate on the cytoplasmic estrogen and progesterone receptors in human endometrial tissues.

We have investigated the effects of including 10 mM sodium molybdate in the buffers used for analysis of cytoplasmic estrogen and progesterone receptors of normal human proliferative endometrium and endometrial carcinoma. Sodium molybdate does not increase the steroid binding capacity of the receptors, but imparts stability to the steroid bound receptor; the steroid-bound receptors in molybdate treated cytosol sediment as distinct 8-9S moieties in sucrose gradients of low ionic strength in contrast to those in untreated cytosol which sediment mainly as 4S. We conclude that sodium molybdate is a useful reagent for the assay and isolation of estrogen and progesterone receptors of human endometrial tissues.