Effect of Parathyroid Hormone and Vitamin A on the Retention of Radiostrontium in the Rat

Abstract

THE experimental data about the influence of parathyroid hormone on the excretion of radiostrontium are ambiguous. Some workers have reported that there is no effect^1–5, others that there is a diminished retention^6–10, and still others claim that retention of radiostrontium is enhanced under the influence of parathyroid hormone¹¹. These discrepancies may be accounted for in a number of ways. Thus the results indicating a positive influence have only been obtained by measuring the urinary excretion of radiostrontium; it is understandable that this slight effect should not be evident in the comparatively insensitive direct determination of radiostrontium in the whole body or the skeleton. Moreover, the capacity of commercial preparations of parathyroid hormone to mobilize calcium from the bone may vary. Finally, most studies so far have been concerned with the administration of parathyroid hormone a comparatively short time after the incorporation of radiostrontium; experiments with calcium-45, however, indicate that the parathyroid influences calcium in the deeper bone areas which are not closely in contact with the easily exchangeable pool^12,13. It follows that the time of administration of parathyroid hormone may affect the results of experiments.