Effects of progesterone on protein metabolism in chicken oviduct tissue pretreated with oestrogen.

1. The effect of simultaneous injections of oestrogen benzoate and progesterone (0.5mg/day each) on immature chicken oviduct tissue pretreated with oestrogen benzoate (0.5mg/day) was studied. 2. After 3 days of treatment with both hormones, the weight of the tissue doubles as compared with tissue treated only with oestradiol benzoate. 3. The progesterone-induced weight increase had no effect on total DNA content of the tissue, but greatly increased the protein/DNA and RNA/DNA ratios. 4. Amino acid incorporation in vivo after progesterone treatment was elevated as measured by using 2h pulses of amino acids; this effect could be accounted for by observed alterations in the concentrations of free amino acids in the tissue. 5. With longer pulses of amino acid the specific radioactivity of total protein remained high in tissue treated with progesterone, at times when specific radioactivity of protein in oestrogen-treated animals was diminishing. 6. From a knowledge of the specific radioactivity of labelled amino acids in the free amino acid pool and in newly synthesized protein, the rate of protein synthesis was estimated in differently treated tissues. 7. The results suggest that progesterone treatment does not cause an increase in protein synthesis. It is concluded that the observed accumulation of oviduct protein is achieved via an effect of progesterone on protein catabolism.