THE EFFECTS OF INGESTION OF HYPERTONIC SALINE ON THE PITUITARY GLAND IN THE RAT: A MORPHOLOGICAL STUDY OF THE PARS INTERMEDIA AND POSTERIOR LOBE

The microscopic changes occurring in the pars intermedia and posterior lobe of the pituitary gland were studied in rats given 2 % sodium chloride in place of tap water for periods ranging from 1 to 21 days. In the pars intermedia small, strongly PAS-positive cells which are normally few in number became very numerous during the first few days of treatment with saline. After longer periods on saline these changes appeared to regress. Mitotic activity in the pars intermedia and posterior lobe was studied using colchicine. Mitoses were present in the pars intermedia of control rats but not in that of salt-loaded rats. In the posterior lobe mitoses were not present in control rats but were numerous in rats drinking saline, and the greatest numbers were seen after 4 days. The neurosecretory material(NSM) was lost from the posterior lobe within the first 8 days, and it is suggested that there is a relationship between the loss of NSM and mitotic activity in the posterior lobe. The significance of the changes in the pars intermedia is not apparent at present but may be related to the removal of neurohypophysial hormones