The C(27)-steroid hormones calcitriol and ecdysterone in the early phase of its action activates hydrolysis of phosphatidylcholines in target animal tissues.

We have examined in vivo the capacities of two C27-steroid hormones--phytoecdysteroid ecdysterone (20-hydroxyecdysone, 10(-8)M) and calcitriol (1 alpha, 25-dihydroxyvitamin D3, 10(-12)M), as a modulators of phosphatidylcholine hydrolysis in the brain and heart cells of rats. Sever lines of evidence indicate that both hormones may acts as positive regulators of membrane phosphatidylcholine hydrolysis by phospholipases A2, C and D in early (0.5-30 min) membrane phase of its actions, yielding known lipid second messengers (diacylglycerol, phosphatidic acid) and soluble products, that may acts as second messengers (choline,choline phosphate, glycerophosphocholine).