Ovalbumin messenger ribonucleic acid accumulation in the chick oviduct during secondary stimulation: influence of combinations of steroid hormones and circannual rhythms.

We have analyzed by hybridization the accumulation of ovalbumin mRNA after the administration of estrogen, progesterone, these two hormones together, or each hormone with testosterone to "withdrawn" chicks (chicks previously stimulated with estrogen but then withdrawn from the hormone). We were interested in determining if the time lag between hormone treatment and a significant increase in ovalbumin mRNA levels could be shortened. After every hormonal treatment we found that there was a 1.5-2.5-h lag period before a significant increase in ovalbumin mRNA levels. This lag period was not simply due to the slow delivery of the hormone to the oviduct. Nuclear estrogen receptor levels had plateaued by 1 h. Rather unexpectedly, the rate of ovalbumin mRNA accumulation after this lag period seemed to depend on the time of the year. Ovalbumin mRNA accumulated faster during the summer and early fall than during the winter and early spring. These seasonal differences were also observed in ovalbumin mRNA levels 24 h after hormone treatment. Such a circannual rhythm may help explain reported differences in the rate of ovalbumin mRNA accumulation during secondary stimulation.