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Lipogenesis in Adipose Tissue from Ovariectomized and Intact Heifers Immunized against Estradiol and(or) Implanted with Trenbolone Acetate¹

Texas A&M University, College Station 77843 and U. S. Department of Agriculture^,3 Clay Center, NE 68933

Abstract

Forty-two heifers were allotted randomly to six treatment groups: 1) intact controls, 2) intact heifers implanted with trenbolone acetate, 3) ovariectomized heifers, 4) ovariectomized heifers implanted with trenbolone acetate, 5) intact heifers immunized against estradiol and 6) intact heifers immunized against estradiol and implanted with trenbolone acetate. Blood titers of estradiol-170 were increased over 100-fold in heifers immunized against estradiol in Freund's complete adjuvant or saline:squalene/arlacel containing Mycobacterium. Lipogenic enzyme activities and acetate incorporation into fatty acids were increased in subcutaneous adipose tissue obtained at slaughter from heifers receiving immunization or the combination of immunization and trenbolone acetate. The increased lipogenic capacity was not reflected in either cell diameter or cells per gram adipose tissue. Ovariectomy in combination with trenbolone acetate caused the lowest activities for all enzymes measured. This treatments also caused the greatest decrease in cell diameter, which resulted in the largest number of cells per gram of adipose tissue. Trenbolone acetate alone had no detectable effect on lipogenesis in the intact heifer, but the combination of ovariectomy and trenbolone acetate caused substantial decreases in enzyme activities, in most cases a significant decrease as compared with ovariectomized heifers. The data suggest that trenbolone acetate is able to depress lipogenesis only when not competing with the effects of circulating estradiol.

¹ Technical article no. 21745, Texas Agr. Exp. Sta. These data have been reported previously in preliminary form. J. Anim. Sci. 61 (Suppl. 1):266, (Abstr. 145).

² Meats and Muscle Biol. Sec, Dept. of Anim. Sci., Texas Agr. Exp. Sta., Texas A&M Univ., College Station.

³ Meat Anim. Res. Center, Clay Center, NE.