Conditions influencing the dose-response effect of growth hormone on longitudinal bone growth in the hypophysectomized rat.

Various factors that might influence the dose-response effect of growth hormone on the longitudinal bone growth were investigated with tetracycline as intravital marker of the bone growth in hypophysectomized rats. These are of practical importance for the bioassay of growth hormone. The growth response was found to be almost the same for subcutaneous and intraperitoneal injection, whereas the intravenous route resulted in significantly lower growth response. The administration of growth hormone in various volumes subcutaneously did not significantly influence the dose-dependent growth response. Freezing of the dissolved growth hormone or addition of NaOH to the solution had no significant effect on growth response. Cortisone acetate 0.5 mg/kg given at hypophysectomy increased the post-operative survival somewhat, without having any post-operative depressing influence on the growth hormone-induced longitudinal bone growth. The present investigation showed that in standardized conditions the dose-dependent growth response is constant.