Development of the oviduct in quail during sexual maturation in relation to plasma concentrations of oestradiol and progesterone.

The macromolecular content (DNA, soluble proteins and ovalbumin) of the magnum and the plasma concentrations of oestradiol and progesterone were studied during sexual development of the Japanese quail. Rapid growth and differentiation of the magnum began between 21 and 28 days of age and rapidly reached the laying stage in about 20 days. This rapid change in magnum size occurred in a stepwise manner: cellular proliferation was observed first, followed by the synthesis and accumulation of specific proteins. Just before and during magnum growth, plasma oestradiol and progesterone concentrations followed different patterns: the initiation of epithelial cell proliferation was preceded by a sharp decrease in plasma progesterone. Maximum cell division occurred while plasma progesterone levels continued to decrease slightly; at the same time, oestradiol increased from 0.098 to 0.453 nmol/l. The decrease and finally the cessation of cell proliferation and the concomitant increase in ovalbumin concentration were related to almost constant levels of plasma oestradiol and increasing levels of plasma progesterone. Further development of the magnum (above 2.3 g weight) involving only the accumulation of secretory products was associated with an increased value of plasma progesterone. These data are consistent with the hypothesis that there are multiple hormonal signals controlling cell proliferation and synthesis of egg-white proteins in the oviduct. Progesterone may be one of the key signals that regulates the initiation of oviduct growth in the quail.