ACUTE ACTION OF CHORIOGONADOTROPIN ON LEYDIG TUMOR-CELLS - QUALITATIVE AND QUANTITATIVE TRANSFORMATION OF LIPID MOIETIES

Background: Testicular Leydig cells use either exogenous or de novo sy nthesized cholesterol as the substrate for the production of testoster one with hormone stimulation, Although the long-term effect of trophic hormones on Leydig cell cholesterol uptake, storage, and deesterifica tion has been well documented, the early effects of the human choriogo nadotropin (hCG) on cell cholesterol/lipid distribution are not yet kn own, Methods: Sections of cells treated with hCG for 15 sec to 30 min were examined by electron microscopy (EM) for the surface density of l ipid moieties in the cytoplasm. In addition, the time-dependent distri bution of lipids within the cytoplasmic inclusions and the ultimate de stination of this substrate were evaluated by ERI, The results were an alyzed with standard morphometric methods, Results and conclusion: The surface density of cytoplasmic lipid pools increased significantly wi thin the 15 sec following the exposure of cells to hCG, and it tapered off to the control level in the subsequent 30 min, Such a fluctuation in the amount of cytoplasmic lipids may be due to (1) the quantity of released substrate from the reticular compartment or (2) the rate of its transport across the outer mitochondrial membrane to the inner mit ochondrial cytochrome P450 side-chain cleavage, where steroidogenesis beans with the conversion of cholesterol to pregnenolone. These two pr ocesses were not quantitatively coordinated in the stimulated cell dur ing the intitial 30 min, resulting in a surplus of cytoplasmic lipid p ools, To compensate for such uneven metabolic balance, the cell appare ntly disposed of the excess substrate by a mechanism of molecular regr ouping from a micellar configuration to a bilayer structure followed b y exocytosis. (C) 1997 Wiley-Liss, Inc.