EFFECTS OF SEX STEROIDS ON HEPATIC AND LIPOPROTEIN-LIPASE ACTIVITY AND MESSENGER-RNA IN THE RAT

In humans, sex steroids have been implicated in the regulation of hepa tic and lipoprotein lipase activity. Therefore, the effects of orchide ctomy and subsequent androgen or estrogen administration on hepatic li pase (HL) and adipose tissue and heart lipoprotein lipase (LPL) were e xamined. Relative to intact controls, orchidectomy of male rats result ed in no significant change in HL activity and mRNA, or in heart and a dipose tissue LPL activity and mRNA levels. Subsequently, a subcutaneo us silastic tubing, delivering either testosterone, dihydrotestosteron e, nandrolone, or 17 beta-estradiol, was implanted for 5 weeks. All su bstitution treatments had a tendency to reduce HL activity and to indu ce HL mRNA levels. This effect was, however, only significant for test osterone which resulted in a decrease in HL activity(238 +/- 15 vs. 32 8 +/- 31 mU/g tissue; p vs. control <0.05) and an increase in HL mRNA( 166 +/- 11 vs. 100 RAU; p vs. control <0.01). No significant effects o f androgens on LPL expression either in heart or adipose tissue were o bserved. Adipose tissue LPL activity(20 +/- vs. 35 +/- 4 mU/g; p vs. c ontrol <0.05) and mRNA(28 +/- 4 vs. 100 RAU; p vs, control <0.001) lev els, but not heart LPL, however, were diminished substantially after 1 7 alpha-estradiol treatment. In conclusion, rat HL is influenced by te stosterone, while adipose tissue, but not heart LPL, is reduced after estrogen administration.