Vasopressin and isoproterenol activate adenylate cyclase in the guinea pig inner ear

Summary Cochleas from guinea pigs were perfused by isotonic buffer after punction of the carotid artery. The cochlea tissue was removed from the bony capsule and separated from the mediolus as band with a sharp needle under the microscope. Cell membranes were prepared subsequently from whole tissue. Purified membranes from the inner ear of guinea pigs contain adenylate cyclase which functionally is coupled with membrane receptors for Vasopressin and- receptors for isoproterenol (epinephrine), respectively. Both hormones stimulate production of cyclic AMP at 37° C.Furthermore, cyclase activity is increased by addition of Gpp (NH)p, a GTP analog. Possible relationships of these molecular events to cochlear events such as glycogenolysis, ionfluxes, transport and secretion mechanisms, and synaptic transmission are discussed.Part of this work was presented at the 15th Workshop on Inner Ear Biology in Seefeld/Innsbruck, Austria, September 3–6, 1978