The importance of biopharmaceutic considerations in biological assays of LHRH and its analogs.

The choice of vehicle, route of administration and actual biological end-point utilized to measure the potency of LHRH analogs can have marked effects on the results of such studies. The activities of LHRH and an analog (D-TRP6,Pro9-NEt-LHRH) suspended in two vehicles were evaluated in two different biological tests including induction of ovulation in androgen sterilized rats and stimulation of uterine growth in immature mice. Our data clearly demonstrate that variables inherent in bioassays used to study LHRH analogs must be controlled if valid conclusions are to be made regarding the relative pharmacological activity and potency of these peptides.