Conformational properties of the opiate peptide C-fragment, and related peptides from lipotropin [proceedings].

found no increase in ribonuclease activity in the postmitochondrial supernatant from the muscle of alloxan-diabetic rats when we followed the conversion of 3zP-labelled rRNA into acid-soluble fragments (Table 1). It is likely therefore that the putative ribonuclease is a relatively specific endonuclease releasing large oligonucleotides which are insoluble in acid. In view of the net breakdown of RNA during diabetes it might have been expected that there would be an increase in the activity of ribonuclease, similar to that seen in dystrophic muscle (Abdullah & Pennington, 1968). However, this does not appear to be the case, for we also found no increase during diabetes in the acid ribonuclease present in unfractionated homogenates of skeletal muscle (L. H. Fahmy & D. P. Leader, unpublished work). It is therefore possible that the loss of skeletal-muscle RNA during diabetes is caused solely by a decrease in the rate of its synthesis, in a manner analogous to that established for the control of the total protein of skeletal muscle (Millward et al., 1976).