Effects of LH and oestrogen on the growth of feminising testicular tumours in mice.

Testicular tumours in mice with testicular feminisation (tfm/y) are made up of masses of large Leydig and lipid-laden cells, surrounded by darkly-stained smaller Leydig cells. The activity of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSDH) is more apparent in the small cells of the peripheral than in the larger cells of the central part of the tumour. Oestrogen alone can stimulate the incorporation of thymidine into deoxyribonucleic acid (DNA) by cultured cells but not the activity of 3 beta-HSDH. On the other hand, luteinizing hormone (LH) promotes activity of the enzyme, but not the synthesis of DNA. Together, they have a greater effect on DNA synthesis and enzyme activity than if present separately. It seems that in tfm/y mice gonadotrophin is necessary for the proper action of oestrogen in control of testicular tumour growth.