ASSESSMENT OF BIOACTIVITY OF WHO NIH RESEARCH STANDARD FOR INHIBIN (CODE 86 690) USING 2 SEPARATE PITUITARY CELL-CULTURE SYSTEMS/

The Research Standard for inhibin, porcine (No. 86/690) distributed by the National Institute for Biological Standards and Control, U.K. for the bioassay of inhibin was tested for its bioactivity in vitro in tw o rat pituitary cell culture systems. The system A was obtained from p ituitaries of 12 day old immature rats while system B was obtained fro m pituitaries of mature male rats. The inhibin preparation failed to i nhibit basal secretion of FSH in the system A. Instead it stimulated t he release of both LH and FSH. 1 ng LHRH induced release of LH was inh ibited by 32, 80 and 43% by 0.1, 1 and 10 IU inhibin, respectively. 10 ng LHRH induced release of FSH was inhibited in a none-dose related m anner and the maximum inhibition was by 10 IU inhibin (25%). The same dose of 10 IU inhibin stimulated LHRH-induced release of LH by 35%. In system B, 1, 10, 50, 100 and 200 IU inhibin suppressed basal secretio n of FSH by 0, 44, 72, 70 and 48%, respectively, while LH was suppress ed by 13, 24, 46, 22 and 21% respectively. The pattern of inhibition o f 10 ng LHRH induced release of LH and FSH by inhibin was similar to i ts effect on basal secretion. A specific dose-related inhibition of FS H was not observed. Our data question the utility of the inhibin stand ard (86/690).