Absence of Appreciable Resistance to Growth Inhibiting Action of Cortisone After Prolonged Treatment.

Abstract

Cortisone acetate was given daily at 4 dose levels, for 50 days, to young female long-Evans rats, initially 38 days of age and weighing approximately 100 g each. The upper 2 dose levels were in the range giving nearly complete cessation of growth. At these 2 levels, there appeared to be a slight reduction in growth inhibiting action after the first 10 days, but all 4 groups still had a marked depression of growth during the 40th to 50th day of treatment. For comparison, anterior pituitary growth hormone and stanolone were given to plateaued adult female rats of the same strain. These hormones, at dose levels capable of giving a major growth response during the first 20 days of treatment, gave little response after the first 20 days.