240 PHILIP SIEKEVITZ 



from the particles, without removal of the RNA from the particles, since 

 the total RNA of these particles has a very low rate of turnover in vivo [5]. 

 This preliminary report notes one of these conditions. In brief, it has been 

 found that the polyamines, putrescine, cadaverine, and particularly sper- 

 mine, will effect a release of the bound enzymes from the particles. In 

 addition, spermine replaces the Mg + + of the particles, and in doing so, 

 confers a stability on the particles in the absence of Mg + +, so that very 

 little or no release of the RNA occurs under these conditions. The con- 

 sequence of these findings on the nature of the bindings among the RNA, 

 protein, and enzymes of the particles is discussed. 



Methods 



The RNP particles of the pancreas were isolated from pancreatic micro- 

 somes by the detergent, deoxycholate, as already described [6, 7]. The 

 measurements of amylase, RNase, and TAPase activities, and the con- 

 ditions for measurements of the release of these activities from the particles 

 has already been given [7], Also, the estimations of RNA, protein, and 

 Mg + +, and the estimations of the release of these from the particles, has 

 been detailed [7]. RNA-P was calculated as being 9% of the RNA, The 

 incubations conditions for the experiments were as follows: The surface 

 of the pellets of the RNP particles was washed, and the particles resus- 

 pended by homogenization in 30% sucrose. Particles from 250 mg. wet 

 weight pancreas were incubated for 30 min. at 35° in a total volume of 

 2-0 ml., containing the various compounds to be tested, and with the 

 final sucrose concentration being 15%. After incubation, the contents of 

 two tubes were pooled, cold distilled water was added, to make the final 

 sucrose concentration 5%, and the suspension was then spun for 90 min. 

 at 105 000 X g in a Spinco Co. refrigerated centrifuge. Enzymic activities 

 were tested on the original particle suspension before incubation, and on 

 the supernatant and sometimes on the pellet after incubation and sedimen- 

 tation. In other experiments, the RNA, protein, and Mg + + contents of 

 the original particle suspension and of the re-sedimented particles were 

 measured. In some cases, where duplicate assays were particularly desirable, 

 as in the Mg + + determinations, more of the incubated particles were 

 pooled for sedimentation. In the cases where radioactive spermine was 

 used, the spun-down pellet was washed several times with cold distilled 

 water to remove possible contamination by unbound spermine and then 

 resuspended in water. In these experiments, one-half of the suspension 

 was used for RNA, protein, and Mg + + determinations, while the other 

 half was dried down on aluminum planchets, kept in a desiccator, and 

 counted with a Nuclear-Chicago gas-flow counter, with a counting error 

 of less than 1%. In these radioactive experiments, about 10 000 c.p.m. 



