Distribution, composition and image analysis of plasma lipoproteins in steroid-treated calves.

Six 8-day-old female calves were treated with a subcutaneous implant of 200 mg testosterone + 20 mg estradiol-17 beta. Thirty-five days following implantation, plasma lipoproteins were compared to those in control calves of the same age. The LDL exhibited a slight change in protein and lipid concentrations and no change in particle size. The effects of steroid therapy on HDL and particularly on the lighter density HDL were characterized by a reduction of densities associated with a decrease in protein content, and by a rise in lipids and an increase in particle size. The changes in HDL composition but not in LDL alterations were consistent with those associated with sexual maturation described previously. Although testosterone is the predominant component of our combined preparation, the effects of our treatment on young female calves is not consistent with the data reported for human lipoproteinemia. The high levels of urinary estradiol in treated calves suggest that these effects result more likely from the aromatization of the injected testosterone.