Testicular Phospholipids: II. Action of Interstitial Cell-Stimulating Hormone (ICSH) Upon Testicular Phospholipids in Hypophysectomized Rats

Abstract

The influence of ICSH in vivo upon the incorporation of 32P (administered in vivo) into testicular phospholipids of hypophy-sectomized rats was studied 20-25 days after operation. The hormone stimulates incorporation of 32P into total testicular phospholipids and into phosphatidyl choline but probably not into sphingomyelin or into phosphatidyl ethanol-amine during the first 4 hr after administration of 32P. The incorporation of choline-3H into phosphatidyl choline was also increased. In addition, however, ICSH stimulates the incorporation of choline-3H into sphingomyelin and of ethanolamine-3H into phosphatidyl ethanolamine. These actions of ICSH were inhibited by anti-ICSH and by treatment of ICSH with urea; both anti-ICSH and treatment with urea greatly reduced the capacity of the hormone to stimulate the incorporation of acetate-14C into testosterone-14C by slices of rabbit testis in vitro. ICSH stimulates incorporation of 32P into total phospholipids of both the interstitial cells and a fraction consisting of seminiferous tubules. On the basis of these observations the following conclusions are reached. 1. ICSH exerts an acute (<2 hr) stimulation on incorporation of 32P and choline-3H into testicular phosphatidyl choline distinct from and not dependent upon FSH, which is known to stimulate the synthesis of testicular phospholipids (3). 2. The action of ICSH upon phospholipids in both interstitial cells and tubules suggests the following mechanism:ICSH→interstitial cells→testosterone→tubules. 3. This proposed mechanism and the differences observed between responses with 32P and tritiated bases warrant further investigation. (Endocrinology86: 1257, 1970)