Induction of Chronic Growth Hormone Deficiency by Anti-GH Serum

Neonatal rats injected from the second through the fifth day of age with monkey antiserum to highly purified rat growth hormone (GH) sustained a chronic inhibition of growth rate and a profound and apparently specific deficiency of pituitary growth hormone. The inhibition of body weight gain by the highest dose of undiluted anti-serum (1 ml) was perceptible as early as 7 days of age and persisted until sacrifice at 78 days of age. At this time, the growth-retarded rats weighed 32% less than the saline controls and were significantly shorter in skeletal length. Their pituitaries were smaller, contained 88% less tibial growth promoting activity, and also displayed a significant reduction in the relative number of acidophils which in 41-day-old males dropped from 40.3 to 29.3% and in females from 39.3 to 32.8% the percentage of basophils or chromophobes was either unchanged or increased. The plasma concentrations of immunoreactive GH were within normal limits both in fed and fasted rats and did not correlate with the profound deficiency of pituitary GH. That the anti-serum specifically affected only pituitary growth hormone was suggested by the negative or minimal effects on pituitary target organs. The anti-serum did show some slight but inconstant effects on the adrenals and gonads and the thyroidal uptake of 131I. The estrous cycles appeared slightly lengthened but the general reproductive status appeared unaffected since the growth-regarded females had normal concentrations of immunoreactive prolactin during diestrus and cast litters of 9 or 10 pups which were of control size at weaning. (Endocrinology95: 793, 1974)