Impaired conversion of @entity35 uterine XXXX receptors during aging.

@entity53 @entity969 @entity35 @entity1329 @entity4338
We have examined the effects of aging on the capacity of @entity35 uterine @entity53 receptors to be transformed from 8S to 4S and 5S species. Cytosol receptors from mature (6-month-old) @entity35 or senescent (24-month-old) @entity35 have been exposed to various @entity4338 concentrations, @entity1329 precipitation and 25 degrees C heating. @entity53 receptors of both the mature and senescent age groups exist in an 8S form on linear 5-20% @entity969 gradients in the absence of @entity4338 and are converted to a 4S molecule in the presence of 0.4 M @entity4338 . At intermediate salt concentrations a greater portion of mature receptors was converted to the 4S species. At 0.15 M @entity4338 62.3% +/- 2.8 of the mature receptors are converted to 4S versus 41% +/- 1.9 of the senescent receptors, and at 0.2 M @entity4338 79.6% +/- 3.2 of the mature receptors are converted to the 4S versus 58.2% +/- 2.1 of the senescent. @entity1329 treatment in the presence of 0.3 M @entity4338 converted about 80% of the receptors from the 4S to the 5S form, while only about half of the old receptors are affected. When @entity1329 precipitates were heated to 25 degrees C all to mature receptors were converted to the 5S species, while only two thirds of the senescent receptors were sedimented at 5S under the same conditions. Inclusion of 20 mM molybdate during preparation blocks conversion of about 15% of the senescent receptors from the 8S to the 4S form but does not affect the mature preparations. Similarly, molybdate treatment does not affect the conversion of the mature @entity53 receptors to the 5S form but increases the percentage of senescent receptors remaining in the 4S form from 30 to 45%. Such qualitative differences in receptor conversion may be related to age associated deterioration of @entity53 stimulated uterine responsiveness.
