Recovery in the Rat from the Diabetes Insipidus Caused by Posthypophysectomy

Abstract

Richter 1 and Pencharz, Hopper and Rynearson 2 have shown that after removal of the posterior lobe of the hypophysis (“posthypophysectomy”) of the rat with minimal damage to the anterior lobe, there ensues a profuse diabetes insipidus. Both were of the opinion that the condition was permanent; Richter followed the water intake of his rats for about 60 days and Pencharz, et al., for 100 days. White, 3 using rats posthypophysectomized by Pencharz, reported 3 animals to be clearly diuretic a year after operation. In our experience, however, recovery from the diabetes insipidus produced by the same operation customarily occurs in time. Fig. 1 shows the excretory records of a group of 50 rats whose urine output was measured in each case at various times postoperatively. It will be noted that in the rat there is no “latent phase” of low fluid exchange such as is seen in the cat and the dog after denervation of the pars nervosa. By approximately 8 weeks after operation most of the rats were excreting urine within the range of the normal animals. Some rats were excreting at normal rates 6 weeks after operation; but others were still excreting above the normal rate for as long as 15 weeks postoperatively. This same slow recovery has also been observed by Dodds, Noble and Williams. 4 Three rats have been observed for 16 months postoperatively. At the end of this period, they were excreting at a rate of 4-6 cc per day—well within the normal range.

Histologic examination of the contents of the sella turcica of these recovered animals showed normal anterior lobe tissue (also, the females had normal estrual cycles). But invariably there was no remnant of pars intermedia.