Electrophysiological and morphological study of endolymphatic sac

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(Electrophysiological Study)The endolymphatic sac direct current potential(ESP)was measured in the guinea pig by means of a glass microelectrode, and the effect of anoxia and various agents on the ESP was examined to know its properties. The results are as follows : 1)The ESP is composed of an anoxia-sensitive part and an anoxiainsensitive part. 2)Canrenoate, an aldosterone antagonist, decreased the ESP in a dose-dependent manner. 3)Acetazolamide, a carbonic anhydrase inhibitor, produced a dose-dependent decrease in the ESP with a saturation of its effect at large doses. 4)Catecholamines reversibly decreased the ESP by beta-adrenergic action. 5)The anoxia-sensitive part of the ESP consists of catecholamine-sensitive and acetazolamide-spnsitve parts.(Morphological Study)Ultrastructure of the endolymphatic sac(ES)in the mouse and the transport of macromolecule in the ES were observed. The results are as follows : 1)The ES in the mouse was divided into three parts : proximal, intermediate and distal. 2)The epithelial cells in the intermediate portion were classified into two types : type I and type II. Type I cells had abundant microvilli, pinocytotic vesicles, vacuoles, multivesicular bodies, lysosomes and mitochondria. Type II cells had fewer numbers of these organelles. 3)The capillaries of the ES were classified as either fenestrated or non-fenestrated. They were botn considered to be permeable to macromolecules. The basolateral absorption in the ES epithelium was considered to be active especially in the intermediate portion.