Demonstration of hCG Binding Sites and hCG Stimulated Steroidogenesis in Different Populations of Interstitial Cells
To gain further knowledge of the mechanism of gonadotropin action in testes, a number of cell purification methods have been employed to isolate the morphologically distinct and biochemically responsive Leydig cells from the variety of cell types found in the testicular interstitium. Centrifugal fractionation of collagenase dispersed cells on density gradients of Metrizamide has been proven to be of considerable value (Conn et al., 1977; Dehejia et al., 1982). Typical Leydig cells were identified in a cell band (density 1.105 g/cm3) which contained a large number of receptors for LH/hCG and responded to the hormone in vitro by producing cAMP and testosterone. A lighter cell fraction (density 1.085 g/cm3) showed cells with a distinct morphology but little hCG binding or steroidogenic response. Similar observations were also reported in mouse testes (Schumacher et al., 1978). Payne et al. (1980a, b), on the other hand, suggested the existence of two distinct populations of hCG responsive testicular interstitial cells. The cells in population I (density 1.085–1.117 g/cm3) produced less testosterone in response to hCG than cells in population II (density 1.128–1.148 g/cm3). The binding affinity for hCG in both populations was, however, the same. All of these observations characterized typical Leydig cells as cells that exhibit high affinity binding of LH/hCG and produce testosterone in response to the hormone.
KeywordsLeydig Cell Interstitial Cell Luteinizing Hormone Receptor Testosterone Production High Affinity Binding Site
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- Ariens EJ, Beld AJ, Rodrigues de Miranda JF, Simonis AM, 1979. The Pharmacon-Receptor Effector Concept: A Basis for Understanding the Transmission of Information in Biological Systems. In: O’Brien RD (ed.), The Receptors, A Comprehensive Treatise. New York: Plenum Publishers, pp. 33–91Google Scholar
- Bhalla VK, Flasch MV, Browne ES, Sohal GS, Sharawy MM, 1987b. Interstitial Cell Heterogeneity in Rat Testes: II. Purification of Cells by Percoll and Metrizamide Gradient Centrifugation with Preferential Localization of Gonadotropin Binding Sites in Light Cell Fraction and Hormone Induced Steroidogenesis in Heavier Cell Fraction. J Biol Chem 262:5322–5332PubMedGoogle Scholar
- Bhalla VK, Haskell J, Grier H, Mahesh VB, 1976. Gonadotropin Binding Factors: Extraction of High Affinity Gonadotropin Binding Sites from Rat Testis and Partial Characterization of Their Interaction with Human Follitropin, Lutropin and Choriogonadotropin. J Biol Chem 251:4947–4957PubMedGoogle Scholar
- Bhalla VK, Powell MM, Rojas FJ, Rajan VP, 1981. Gonadotropin Binding Model: Comparison of the Binding Characteristics of cAMP to Protein Kinase Holoenzyme and Gonadotropin to Particulate Receptors in Rat Testis. In: Mahesh VB, Muldoon TG, Saxena BB, Sadler WA (eds.), Functional Correlates of Hormone Receptors in Reproduction. New York: Elsevier North Holland Inc. pp. 419–436Google Scholar
- Bhalla VK, Rajan VP, Burgett AC, Sohal GS, 1987a. Interstitial Cell Heterogeneity in Rat Testes: I. Purification of Collagenase Dispersed Leydig Cells by Unit Gravity Sedimentation and Demonstration of Binding Sites for Gonadotropin in Light Cells Versus Enhanced Steroidogenesis in Heavier Cells. J Biol Chem 262:5313–5321PubMedGoogle Scholar
- Boeynaems JM, Dumont JE, 1975. Mini Review Quantitative Analysis of the Binding of Ligands to Their Receptors. Journal of Cyclic Nucleotide Res 1:123–142Google Scholar
- Hechter OM, 1978. The Receptor Concept: Prejudice, Prediction, and Paradox. In: Klachko DM, Forte LR, Franz JM (eds.), Hormone Receptors. New York: Plenum Press, pp. 1–44Google Scholar
- Leuschen M, Tobin R, and Moriarty M, 1978. Enriched Populations of Rat Pituitary Thyrolrophs in Monolayer Culture Endocrinology 102:509–518Google Scholar
- Pollet RJ, Levey GS, 1980. Principles of Membrane Receptor Physiology and Their Application to Clinical Medicine. Ann of Internal Med 92:663–680Google Scholar
- Pretlow II TG, Pretlow TP (eds.), 1982. Cell Separation, Methods and Selected Applications. New York: Academic Press, Vol. IGoogle Scholar
- Rodbell M, 1971. Hormones, Receptors, and Adenyl Cyclase Activity. In: Condliffe P, Rodbell M (eds.), Colloquium on the role of Adenyl Cyclase and cAMP in Biological Systems. Fogarty International Center, Gov’t Printing Office, Washington, D.C. pp. 88–95Google Scholar
- Triggle DJ, 1978. The Receptor Theory. In: Smythies JR, Bradley RJ (eds.), Receptors in Pharmacology. New York: Marcel Dekker Inc., pp. 1–66Google Scholar