Temperature Acclimation Effects on Monkey Liver RIBO- and Deoxyribonucleic Acid and on Ribonucleic Acid of Other Organs. ∗

Summary

Studies were made to determine the influence of cold and heat acclimation on the RNA content of the heart, liver, pancreas, kidneys, and cerebral hemispheres in the squirrel monkey (Saimiri sciurea). Total DNA was assayed, and liver RNA: DNA ratios were calculated. The total amounts of RNA in the kidneys, heart, and pancreas were increased as a consequence of cold acclimation: in the kidneys and heart proportionally to the increase per g protein, but in the pancreas—the organ which showed greatest change in RNA content—there was an increase in RNA per g protein. Since greater amounts of food are consumed in the cold, necessitating enhanced insulin and digestive enzyme secretions, the outflow of these proteins probably prevents a percentage protein accumulation in the pancreas equal to that of RNA. Cold exposure produced a significant increase in total DNA and total protein in the liver which may be due to hepatic cell proliferation. However, there was no increase in total liver RNA which, among other possibilities, might indicate a suppression of DNA transcription or an enhanced RNAase activity. Heat acclimation resulted in lower total protein in the liver and pancreas with no alterations in the heart or kidney protein levels. None of these organs exhibited a decrease in RNA per g. However, a decrease in total RNA proportional to the decrease in protein content was seen in the liver and pancreas; whereas no change in total protein or in total RNA occurred in the heart or kidneys. There were no changes in cerebral RNA per g protein consequent to either heat or cold acclimation.