Detection of hormone-sensitive lipase in various tissues. II. Regulation in the rat testis by human chorionic gonadotropin.

Abstract

Hormone-sensitive lipase (HSL) is an intracellular neutral lipase found in a variety of tissues, primarily in adipose and steroidogenic tissues, that hydrolyzes triglycerides and cholesteryl esters. In the rat testis steady-state levels of HSL mRNA increase dramatically during sexual maturation. In addition, HSL-like immunoreactive proteins of 84, -89, and -102 kD have been observed in sexually immature rats with additional -113 and -127 kD immunoreactive proteins expressed in mature animals. In the present studies the ability of human chorionic gonadotropin (hCG) to regulate the expression of HSL and HSL-like immunoreactive proteins in rat testes has been examined. Treatment of sexually immature rats with daily injections of hCG caused a gradual increase in HSL activity that reached an 80% rise (P < 0.01) after 5 days. This was paralleled by a 3-fold increase (P < 0.01) in the 84 kD protein representing the active HSL enzyme. The -89 kD immunoreactive protein was also increased -5-fold (P < 0.01) in parallel to the 84 kD protein and HSL activity. The -102 kD immunoreactive protein was increased by hCG treatment (P < 0.01); however, its expression did not follow changes in HSL activity or in the 84 and -89 kD immunoreactive proteins, peaking within 12 h and declining thereafter. The -113 and -127 kD immunoreactive proteins did not appear during the 5 days of hCG treatment. Steady-state levels of HSL mRNA increased 60-100% (P < 0.02) in parallel to the changes in HSL activity and in the 84 and -89 kD immunoreactive proteins.(ABSTRACT TRUNCATED AT 250 WORDS)