Mechanisms subserving insulin action in the gonad: Evidence that insulin induces specific phosphorylation of its immunoprecipitable receptor on ovarian cells

To test the capacity of insulin to work through a classical insulin-receptor pathway in the ovary, cultured swine granulosa cells were treated with insulin and/or increasing concentrations of insulin-receptor antiserum. Insulin-receptor antiserum but not control serum significantly (>85%) attenuated insulin's stimulation of progesterone biosynthesis. Moreover, in broken-cell preparations, insulin but not desoctapeptide insulin or somatomedins induced specific phosphorylation of the 95,000-dalton, immunoprecipitated beta subunit of the insulin receptor on ovarian cells. These observations provide the first evidence for discrete biochemical actions of insulin at the level of the cell-membrane receptor for insulin in gonadal cells.