AMP is a component of the low molecular weight mitogenic activity present in human pituitary tumours

The mitogenic activity of extracts of human non-functional pituitary tumours has been studied. Previously we have reported that the tumour extracts could be resolved into both high (> 13,000) and low (< 3,000) molecular weight fractions using Sephadex G-50 chromatography. Mitogenic activity was assayed by looking at trichloroacetic acid precipitable 3H-thymidine incorporation into GH3 cells. We have now purified the major component of the low molecular weight mitogenic fraction using reversed phase HPLC: the material was identified and found to be 5'-adenosine monophosphate (5'-AMP) using electron spray mass spectrometry. The mitogenic activity of 5'-AMP and the purified tumour extract was confirmed as both produced an increase in GH3 cell number after 4 days of treatment. In conclusion our results show that the major component of the low molecular weight mitogenic activity in human non-functional pituitary tumour extracts is 5'-AMP.