Abstract
The first evidence suggesting any endocrine function for the pituitary gland was presented in a short paper by Oliver and Schafer (1895) which described the pressor effect of an aqueous extract of the gland (24). Subsequent research has resulted in the morphological division of the Pituitary Gland into the neurohypophysis and adenohypophysis, identification of the various hormonal products and elucidation of their physiological role (2,3). | At present six substances have been extracted from the anterior lobe (adenohypophysis) of the pituitary gland, which are generally acknowledged to be physiologically important hormones; the three gonadotrophins,, follicle-stimulating hormone, luteinizing hormone or interstitial cell-stimulating hormone, and in some species prolactin; two other trophic hormones—adrenocortrophic hormone and thyroid-stimulating hormone, and somatotrophin or growth hormone (STH or GH). | The intermediate lobe of the gland was found to elaborate the chromophore hormone in many species of lower animals. | It is generally believed that the pituitary posterior lobe is the storage site of the two octopeptides, oxytocin and vasopressin which are produced by the supraoptic and paraventricular nuclei of the hypothalamus. Oxytocin is a powerful stimulant of the pregnant uterus, especially toward the end of gestation and seems to have an important role in lactation. Oxytocin also shares many of the actions typical of vasopressin which is described in the following review of the literature. | It now appears that vasopressin may have effects on the kidneys, smooth muscle and in general on cellular membrane permeability. Vasopressin exerts at least three actions on the kidney: (a) it controls the permeability of the distal convoluted tubules and collecting ducts to water; (b) it may stimulate the pumping of sodium by the loops of Henle; (c) it may regulate the rate of blood flow through the peritubular capillary network (25). | Recent studies on frog skin and toad bladder indicate that vasopressin influences the movement of water and electrolytes by increasing the permeability of the cell membrane (18). |In pharmacological amounts, vasopressin causes contraction of smooth muscle tissues in various organs. The following section will give a short summary of the literature of this action upon the smooth muscle of the cardiovascular and gastrointestinal system, gall bladder, uterus, mammary gland, epididymis, vas deferens and ureter. The studies found in the literature on the urinary bladder will be treated in greater detail.