Studies on progesterone receptors during protein malnutrition and steroid maintained pregnancy in rat

The distribution pattern of progesterone receptors (PR) in nuclear and cytoplasmic compartments of uterus and factors affecting the PR levels were studied. The concentration of nuclear PR was decreased significantly on day 15 and 20 of dietary protein restriction, both in non-mated and mated rats. However, a marked decline in cytosol PR levels was observed only in non-mated protein-free diet (PFD) rats. During steroid-maintained pregnancy the concentration of PR in uterine nuclei was significantly higher on day 15 of gestation than those obtained on day 20. In contrast, the levels of PR in cytosol, were much higher on day 20 of gestation in steroid maintained as well as normal pregnant rats. The translocation studies revealed that the magnitude of translocated PR complex to the nucleus (at 3 h) was more pronounced in protein deficient rats and the time-dependent replenishment of cytosol PR was not observed in above group, as proposed for estrogen receptors. Administration of estradiol 17-beta to PFD-rats resulted in an increase in cytosol PR without altering the nuclear PR levels. In addition, protein deficient rats exhibited a higher Kd value than normally fed rats. In conclusion, it can be suggested that these fluctuations in uterine PR are related to changes in endogenous hormone levels and binding affinity of receptor molecules.