Methyltestosterone, testosterone or dl-ethionine administration to dogs causes marked reduction in high density -S1.21 0–20 (alpha) lipoproteins. Lower density -S1.21 25–40 or 40–70 (Sf 12–20 or 20–100 or beta) lipoproteins are not found in sera from healthy dogs and therefore cannot increase in amount during androgen administration, as is often the case in human subjects. In the dog, reduction in -S1.21 0–20 serum lipoprotein levels therefore is accompanied by reduced levels of serum cholesterol and phospholipid. The liver total lipid, cholesterol and lipid phosphorus values did not change, in spite of marked changes in serum values, after testosterone or dl-ethionine administration. Our failure to find fatty livers in the dogs fed dl-ethionine may be attributable to the fact that the animals were not force-fed. Since androgen appears to protect many species against fatty liver induced by dl-ethionine, presumably by a protein-sparing action, it is suggested that the reduction in canine serum lipids and lipoproteins induced by dl-ethionine and androgens must result from either a) different mechanisms, or b) if a common mechanism, then one not involving ‘protein metabolism’ per se.
