Synthesis of Protein in the Pancreas

Abstract

1. The ribonucleoprotein of the microsome fraction which sediments at 40,000 R.P.M. as a pellet (and which is referred to as the pellet material) has been studied with reference to its role in protein synthesis in the pancreas. 2. In pellet material nucleic acid and protein form a definite complex as shown by its electrophoretic behavior and unchanging composition under various conditions. 3. Protein of pellet material is not especially rich in the diamino acids. 4. Evidence is brought forward indicating that the protein component of pellet material takes part in the general process of protein synthesis in the cell. (a) The well known correlation between quantity of RNA and rate of protein synthesis in a tissue implicates the protein of the pellet material, for most of the RNA in the pancreas and other tissues is in this material. (b) Uptake of isotopically labelled glycine by the pellet material, confirming results of previous workers, is for short periods greater than in other protein fractions. (c) Comparing the pellet materials of pancreas, liver, and kidney—three tissues with vastly different rates of protein synthesis, in the sequence given—there is a correlation between the quantity of RNA in the pellet and the rate of protein synthesis in the tissue; a similar correlation between quantity of RNA in the pellet material and rate of N15-glycine uptake by the protein component of the pellet; and finally, the level of uptake by total protein varies with the tissue and is related to the uptake of N15-glycine by protein of the pellet. 5. In the pancreas a distinction can be made between proteins synthesized for secretion and the nucleoprotein of the pellet (not found in the secretion) which, however, takes part in the synthetic process, as shown by the fact that the N15 uptake by protein of the pellet is increased when the synthesis of digestive enzymes is stimulated by secretion. 6. The time course of N15 uptake by proteins of the pancreas indicates that pellet protein serves as precursor material in the synthesis of the secretory proteins. 7. Rate of uptake of N15-glycine by the purines of RNA of the pellet material is not correlated with uptake by the protein. 8. The uptake of C14-alanine by an in vitro system of microsomes + mitochondria is impaired by preincubation of the microsomes with ribonuclease. This is direct experimental evidence for the dependence of protein synthesis upon the presence or intactness of ribonucleic acid in the microsomes.

Effect of caerulein on protein synthesis and secretion in the guinea‐pig pancreas

“…Several conflicting results concerning the effect of stimulation of pancreatic secretion on the rate of protein synthesis have been published in the past (Daly & Mirsky, 1953;Allfrey et al, 1954;Ferreira et al, 1955 ;Farber & Sidransky, 1956;Hokin, 1956;Busch et al, 1959;Stocker, 1962;Webster & Tyor, 1966;Peakall, 1967;Webster, 1968;Kramer & Poort, 1968;Poort & Geuze, 1969;Poort & Kramer, 1969). As pointed out by Poort & Kramer (Kramer & Poort, 1968;Poort & Kramer, 1969) it is possible to reconcile most of the discrepancies by taking into account the fact that in a protein-secreting gland the amount of protein present Values given are averages ±S.E.…”

“…Numerous studies dealing with the effect of stimulation of enzyme secretion on the rate of protein synthesis in the pancreas have been reported (Daly & Mirsky, 1953;Allfrey, Daly & Mirsky, 1954;Ferreira Fernandez & Junqueira, 1955;Farber & Sidransky, 1956;Hokin, 1956;Busch, Allen & Anderson, 1959;Stocker, 1962;Webster & Tyor, 1966;Peakall, 1967;Webster, 1968;Kramer & Poort, 1968;Poort & Geuze, 1969;Poort & Kramer, 1969). Though several conflicting results have been obtained in the past, recent studies seem to indicate that a substantial increase of the rate of protein synthesis is brought about by either feeding or pharmacological stimulation of secretion only in birds and frogs (Webster & Tyor, 1966: Peakall, 1967Webster, 1968;Poort & Geuze, 1969); whereas in mammals protein synthesis proceeds at a constant rate, independently of secretion (Kramer & Poort, 1968;Poort & Kramer, 1969).…”

Radioselenium in Duodenal Aspirate as an Assessment of Pancreatic Exocrine Function

“…Radioactive labelled amino-acids given intravenously to experimental animals are rapidly taken up by the acinar cells of the pancreas (Allfrey et al, 1953;Junquiera et al, 1955). Hansson (1959) gave intravenous 35S-methionine to a variety of experimental animals and showed preferential uptake of the aminoacid by the pancreas, the radioactivity per gramme of tissue in this organ being six to eight times that in the next most active oigan, the liver.…”

Alkaline Phosphatase in the Dorsal and the Ventral Halves of the Iris During Early Stages of Lens-Regeneration in the Newt

“…It is now well-established that alkaline phosphatase is particularly rich in the cells which are engaged in the synthesis of fibrous protein (JOHNSON et al 1945, BRADFIELD 1946, JEENER 1948, and ELLIS et al 1956, and that the presence of ribonucleic acid (RNA)-protein is an essential factor for protein synthesis (ALLFREY et al 1953, BORSOOK 1954, GALE and FOLKES 1954, ZAMECNIK and KELLER 1954, ALLFBEY et al 1955, BRACHET 1957, MIURA et al 1957and STICH and PLAUNT 1958. Moreover, an intimate association of alkaline phosphatase with RNA in the synthesis of fibrous proteins has been pointed out by some workers (BRACHET 1942, FELL and DANIELLI 1943and BRADFIELD 1950, POSALAKY et al (1951) reported that in the lens-regenerating process of the newt, the activity of alkaline phosphatase increases gradually in the retina, recording a peak on the 14th day after lens-extirpation and then decreases to the level of the non-operative eye.…”