Immunocytochemical and Morphometric Studies on the Effects of Dehydration on Vasopressin-Secreting Cells in the Hypothalamus of the Mongolian Gerbils

Abstract

Effects of dehydration on vasopressin-secreting cells (VP cells) of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) in the Mongolian gerbils were studied immunocytochemically and morphometrically. The plasma osmolality was measured at the time of sacrifice of individual animals and the body weight was measured every day during dehydration. The plasma osmolality increased significantly on day 3 of dehydration, followed by a gradual increase to reach nearly its equibilium state on day 10. The body weight decreased rapidly until day 10, followed by a gradual decrease thereafter. The area of VP cells increased significantly in both the SON and PVN on day 1 of dehydration, the level being nearly the same until days 3 to 5 and going up on day 7 to reach the plateau after day 15. These findings seem to reflect a compensation mechanism between the volume of body fluid and the plasma osmolality and to reflect responses of VP cells to the osmotic stimuli. Electron microscopic observation revealed that, at the beginning and late stages of dehydration, the increase in the area of VP cells was in parallel with the expansion of the Golgi area and with the distension of cisternae of the rough endoplasmic reticulum.