Determination of rat 5alpha-reductase type 1 isozyme activity and its inhibition by novel steroidal oxazolines.

The 5alpha-reductase type 1 isozyme is a key enzyme in the metabolism of the androgen steroid hormones and inhibitors of this enzyme represent a new pharmacological treatment for several androgen dependent diseases. We developed a radiosubstrate in vitro incubation method for the determination of 5alpha-reductase type 1 activity using rat liver microsomes as an enzyme source. With this method we have studied the inhibiting activity of novel (5' S)-17beta-(4,5-dihydrooxazol-5-yl)androst-5-en-3-one compounds containing various derivatized phenyl substituents coupled to the exo -heterocyclic moiety. Tests revealed moderate inhibitory actions compared to finasteride, nevertheless, results provide interesting structure-activity relationship data.