Sweat glands increase their activity. The smooth muscles of the arterioles dilate, reducing resistance and thus lowering blood pressure. In the presence of ADH, the distal convoluted tubule and the collecting ducts become more permeable to water. The ADH molecules bind to the receptor molecules on the cell membranes of the epithelial cells of the distal convoluted tubules and the collecting ducts. Once bound, the cells increase the rate of cyclic AMP synthesis, which increases their permeability to water.
Water thus moves out of the tubules and ducts by osmosis into the interstitial spaces.
This movement of water causes a decrease in volume of filtrate in the nephron and thus an increase in its concentration. In A.C. Guyton and J.E. Hall, Textbook of Medical Physiology. W.B. Saunders Company, Philadelphia. Seeley R.R. 1995. In R.R. Seeley, T.D. Stephens and P. Tate, Anatomy and Physiology.