Responsiveness to Lipolytic Hormones, and Inactivation of Adrenocorticotropin, by Adipose Tissue Slices and Free Fat Cells from Different Mammalian Species

Abstract

The adipose tissues of rat, hamster and guinea pig are known to differ from each other in capacity to respond to the lipolytic action of adrenocorticotropin (ACTH), β-melanocyte-stimulating hormone (β-MSH), thyroidstimulating hormone (TSH), glucagon and epinephrine, and in capacity of the homogenized tissue, to destroy the lipolytic activity of ACTH and other lipolytic pituitary peptides. In order to learn whether these species differences reside in the fat cells, or in other components of the adipose tissue, (a) adipose tissue slices and free fat cells (prepared by the collagenase technique of Rodbell) from the same rat, hamster or guinea pig were incubated with ACTH, β-MSH, TSH, glucagon or epinephrine, and the lipolytic response was measured; (b) aqueous homogenates of adipose tissue and free fat cells from the same rat or hamster were incubated with ACTH and the effect of the incubation on the hormone’s lipolytic activity was measured. The data show that, in all 15 instances tested, the free fat cells possess the same pattern of responsiveness or unresponsiveness to lipolytic hormones as does the adipose tissue slice; and that the capacity of rat and hamster adipose tissue to inactivate ACTH is largely recovered in the free fat cell fraction of the tissue. (Endocrinology85: 209, 1969)