Development of Resistance to Growth Promoting Action of Anterior Pituitary Growth Hormone

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Abstract
Groups of adult female Norway rats were treated with constant dosage of 4 different growth hormone preparations. Two of these preparations were highly purified, one was crystalline but contained appreciable contaminating nitrogenous material. The 4th preparation was a crude extract prepared by mild extraction, calculated to reduce alteration of the protein during extraction. In all 4 experiments the treated rats grew rapidly at first, then more slowly and finally attained growth plateaus as flat as the non-treated controls. Increasing the dosage resulted in renewed growth followed by plateauing at a greater weight. Blood sugar determinations on one of the groups indicate that any response to the diabetogenic action of growth hormone was extremely mild in these animals both during the period of rapid growth and after near cessation of the growth response.