Effects of hormones on the renal response to unilateral nephrectomy in hypophysectomized rats

The roles of selected hormones in restoring the capacity of the remaining kidney following uninephrectomy of hypophysectomized rats to respond by tubular hyperplasia were explored. Autoradiography, using tritiated thymidine, was employed for identifying cells synthesizing new deoxyribonucleic acid within a standard period, a valid measure of mitotic activity. For animals with intact pituitary glands, both cortex and medulla of kidneys remaining three days after uninephrectomy exhibited a 3½‐fold increase in numbers of labeled cells over control levels. The amount of mitotic activity in either region of bilaterally intact kidneys of hypophysectomized animals was not significantly different from that for animals with intact pituitaries, but the compensatory renal hyperplastic response to uninephrectomy was reduced to one‐third. Either a small amount of growth hormone or a much larger amount of anterior pituitary extract, administered subcutaneously twice daily for several days, restored the compensatory response to uninephrectomy to levels obtained in rats with intact hypophyses. Adrenocorticotropic hormone depressed mitosis markedly in control kidneys of hypophysectomized animals and to an even lower level in remaining kidneys. Growth hormone would appear to be a necessary and effective component of the pituitary secretion in permitting compensatory renal hyperplasia to take place. Since prior studies have shown adrenalectomy to promote cellular division in renal tubules, it was assumed that the presently reported depression of renal mitosis by excess adrenocorticotropic hormone was mediated by an overactivity of the adrenal glands.