Pituitary and Serum Growth Hormone During Undernutrition and Catch-up Growth in Young Rats

Abstract

Sprague-Dawley rats at birth were redistributed among nursing mothers, 4 to some, 16 to others. After 21 days, they were studied by sex and by nutritional state using a heterologous radioimmunoassay for growth hormone (GH) content of pituitary gland and plasma. Greater access to milk resulted in mean body weights of males and females of 63 ± 1 g contrasting with 34 ± 2, p < 0.01,and pituitary weights of 3.0 ± 0.07 mg, contrasting with 2.0 ± 0.06, p < 0.01. Better nutrition was attended by plasma GH of 34 ± 14 ng/ml, in contrast to 14 ± 2 ng/ml in the undernourished. There were highly significant differences in total pituitary growth hormone (257 ± 12 μg/gland in well-fed; 88 ± 6 μg/gland in the undernourished). During two weeks of free access to food, the rats from the 16 per mother group grew at 5 times their previous rate (7.5 g per day vs 1.5 g) and nearly overtook the previously better-fed group; plasma growth hormone with dietary repletion was the highest observed, and pituitary weights and growth hormone contents per gland equalized. Rat growth hormone synthesis by pituitary explants was studied in vitro, and, judged by incorporation of 3H-leucine into GH, glands from well-fed rats at 17 days age showed significantly greater rates of synthesis than glands from undernourished rats. (Endocrinology92: 1768, 1973)