Rapid changes in the synthesis of specific ovarian granulosa cell proteins induced by human choriogonadotropin

Total ovarian granulosa cell proteins were labeled in vitro with [35S]methionine and analyzed by two-dimensional polyacrylamide gel electrophoresis. Of the 100-150 distinct proteins resolved by this method, 1-2% demonstrated an observable change in their synthesis during the early phases of luteinization after hormone administration. Two specific proteins first appeared as early as 30 min after treatment with human choriogonadotropin, while four additional new proteins became apparent at 3 hr. These changes in the synthesis of specific proteins occurred far in advance of the morphological changes associated with luteinization, which occur 24-72 hr later, and thus may play an important role in this process of hormonally induced cell differentiation in the rat ovary.