Hormonal influences on the growth and enzymic differentiation of the small intestine of the hypophysectomized rat

Abstract

When rats are hypophysectomized in neonatal life, the growth of the small intestine is more severely retarded than the growth of the body as a whole. It was shown previously that intestinal growth is not rectified by doses of cortisone and/or throxine that restore normal activity of brush border enzymes in hypophysectomized sucklings; growth hormone did not affect relative weight or enzyme activity. Reexamination of this problem with much lower doses of hormones than previously employed has now shown that relative weight of the intestine is enhanced by cortisone and thyroxine together, and is normalized by cortisone and thyroxine in combination with rat growth hormone. Growth induced by treatment with the three hormones involved increases of crypt depth and villus height, and of mitotic index. Body weight was not affected by hormonal treatment, but the tails of the hypophysectomized sucklings were significantly lengthened by thyroxine alone, the effect being enhanced when growth hormone was also given. The physiological dose of hormones used in the present study were as effective in elevating activity of alkaline phosphatase and sucrase as the larger doses previously used. Cortisone had a greater effect on sucrase, thyroxine on phosphatase. Pentagastrin did not influence either growth or enzyme activity.