Failure of Posterior Pituitary Hormone Samples of Low Metal Content To Produce Mitochondrial Swelling¹

Abstract

8-Lysine-vasopressin and oxytocin samples of low metal content were tested for their ability to produce swelling of isolated rat liver mitochondria. The results indicate that,-contrary to previous claims, the posterior pituitary hormones are not potent mitochondrial swelling agents. (Endocrinology 83: 368, 1968) W E HAVE reported (1) that the mitochondrial swelling effects of 8-lysine-vasopressin samples are largely, if not entirely, attributable to metal contaminants in the samples, rather than to previously postulated reactions involving the hormone's disulfide group (2). We pointed out, however, that participation of the disulfide group could not be completely eliminated from consideration until the absence of swelling activity could be demonstrated in hormone samples free from significant amounts of metal contaminants. We have recently tested such samples of 8-lysine-vasopressin and oxytocin for their ability to produce swelling of isolated rat liver mitochondria. The results of this study, reported here, indicate that the posterior pituitary hormones are devoid of swelling activity and suggest that the effects observed previously in other laboratories (2-4) were artifactual. Materials and MethodsMitochondria were prepared from rat liver and swelling experiments were performed as described previously (1, 5).8-Lysine-vasopressin sample 1 was isolated from hog posterior pituitary glands several years ago by Dr. Andrew V. Schally and given to Dr. Vincent du Vigneaud. At the time these experiments were performed, this preparation possessed a pressor activity (6) of approximately 200 units/mg.