The objective of this research proposal is to examine the responsiveness of the rat uterus during the period of reproductive decline. The experiments are divided into two major areas. Firstly, the induction of two uterine enzymes, glucose-6-phosphate dehydrogenase (G6PD) and ornithine decarboxylase (ODC) after hormonal stimulation or induction of deciduomata will be examined for a faulty or delayed response. Secondly, the effect of increasing age on the concentration of "altered" proteins will be examined. The objectives will be accomplished by determining the kinetics of induction (lag time before increase, rate of increase, maximal levels attained) of uterine G6PD and ODC after estradiol administration. The levels of uterine enzymes during hormonal preparation for the decidual response will be compared in young and old animals. The presence of altered enzymes in senescent uteri will be determined using differential heat stability of enzyme and comparative immunotitration.