THE RELATION BETWEEN AGE AND THE B/A CELL RATIO IN THE ISLET TISSUE OF THE RAT

Abstract

The ratio between the number of B and A cells has been estimated in 60 male rats at ages ranging from new-born to 480 days. The animals were fed a diet yielding 38% calories from carbohydrate, 24.5% from fat, and 37.5% from protein. In the new-born rats relatively more A cells were observed than in adult animals. Later in life the B/A cell number ratio was surprisingly constant except in the case of the oldest animals. The relative decrease in B cells in this oldest age group is similar to the decreased ratio reported for man. Small islets contain relatively more B cells than large islets. Dominance of B cells in the small islets was most pronounced in the adult animal. The necessity of combining the differential counts with karyometric measurements is stressed. The systemic error which occurs without a correction for variation in nuclear size lies between 4.3 and 10.6%.