Asolectin decreases progesterone inhibition of oocyte adenylate cyclase

Asolectin, a naturally occurring mixture of soybean phospholipids, causes a small (10-25%) but reproducible stimulation on the activity of oocyte adenylate cyclase measured in the presence of guanine nucleotides. This phospholipid preparation, at a concentration of 0.5-1 mg/ml, greatly reduces the inhibition of this enzyme caused by progesterone. The reversal of the progesterone inhibition is due in part to the effect of asolectin in reducing the hysteresis of the enzymatic reaction which is enhanced by progesterone. The asolectin effect is not due to trapping of the progesterone and making it unavailable for interaction with its receptor, because similar concentrations of the phospholipid do not prevent the induction of meiotic maturation of the oocytes by progesterone. This finding suggests that the phospholipids interfere with the transduction of the hormonal signal to the adenylate cyclase catalytic subunit.